Despite an Alfie Bavidge double, the young Dons were hit with a late sucker punch as Hearts edged a five goal encounter at the Oriam, Mackenzie Kirk's 90th minute header securing the points for John Rankin's young Jambos.
After Friday's setback at Motherwell, the young Dons were quickly back in action as they travelled to the Oriam to face a Hearts side who moved up to second place in the CAS Under 18 League after a fine 3-1 win over Dundee United.
Barry Robson's side showed two changes from last week's staring eleven as Jamie Shingler and Taylor Mason came in for Blessing Oluyemi and Blair McKenzie who dropped to the bench.
Shingler was the first keeper called into action, blocking well from Kirk. At the other end, Adam Emslie had a glimpse of goal but was closed down before he could get a shot away.
A quick Hearts break saw Finlay Murray make an excellent interception to prevent McLuckie's cross finding a striker in maroon. The home side were enjoying the bulk of possession on the big pitch without applying roo much pressure to the Aberdeen defence.
Evan Towler's powerful defending was well to the fore as he held off three Hearts players before clearing the ball up the park, the big lad improving steadily game by game.
McLuckie again looked dangerous going down the left but Mason's calm header back to his keeper nipped the danger in the bud.
Finlay Lobban forced a fine save from McFarlane on 21 minutes, the keeper tipping his 25 yard free kick past the post.
The Dons took the lead in the 25th minute, Alfie Bavidge knocking the ball in from a yard out after Murray's shot from a corner had been deflected on to the bar. Against the run of play maybe, but nonetheless welcomed by the visitors.
Bavidge was looking to double his tally three minutes later when he raced on to a neat Ethan Duncalf pass, but his fierce shot was too high.
A handling error from Shingler presented Kirk with a sight of goal, but he fired wildly over. A let off for the Dons who had looked solid defensively in the first half hour, exemplified by Towler's goal-saving block to deny Pollock after a wonderful pass from Thomas.
Great determination from Bavidge saw him won a ball he had no right to reach and his pass found Emslie with a clear shot at goal, but the winger crashed the ball off the top of the bar instead for doubling Aberdeen's advantage.
Ross fired wide for Hearts as the interval approached but there was still time for another Dons chance, Emslie shooting wide after fine work down the right by Lobban and Duncalf.
A solid first half showing from the Dons who, despite having less possession, created the better chances and perhaps should be leading by more than one at the break.
Half time - Hearts 0 Aberdeen 1
Hearts introduced Sandilands for Thomas at the break while Blair McKenzie replaced Finlay Murray who had taken a knock in the opening period. And it was the Hearts man who made an impact smashing a loose ball past Shingler from 20 yards to make it all square on 47 minutes.
And it got even better for the homesters as they took the lead on 54 minutes, a cross from Sandilands being cleverly dummied to allow the lurking Pollock to slam the ball home from six yards.
Barry Robson immediately introduced Ryan Duncan and just beyond the hour his cross was punched clear only as far as Finn Yeats who volleyed narrowly wide.
Balls over the top of the Hearts defence were causing problems and Emslie nearly profited but keeper McFarlane was fast off his line to block the winger.
Aberdeen kept pushing forward and they were rewarded with a minute of normal time remaining as Bavidge cleverly headed home after a collision between Harvey and the keeper as they battled to get to Duncan's cross.
However, there is an old saying in football that you are at your most vulnerable just after you have scored and so it was to prove unfortunately for the Dons.
A short corner move saw Pollock swing in a cross which was met powerfully by the head of Mackenzie Kirk and his effort found the net via the underside of the bar.
So, another defeat on the road, but the general opinion, even of the home fans, was that the better team lost. No consolation however for Aberdeen whose next assignment is a Cormack Park meeting with Hamilton Accies on Friday.
Full time - Hearts 3 Aberdeen 2
Barry Robson: "I think we still lack a bit of confidence from the last game. I think you could see that tonight defensively and we were not helped when Finlay Murray has to go off injured at half time and then we are playing with a new back four again.
"There has been a lack of consistency in section due to defenders not being available and I think it shows. We have lacked a bit of fluency in the game because of it.
"But we should still not be conceding a last minute winner like we did. You are always at your most vulnerable when you have just scored so that was very frustrating.
"In the first half, despite not being at our best, we take the lead and control parts of the game and looked the most dangerous team. We looked like the team that would score goals.
"I thought we coped well with their shape. We like to be more possession based but we gave up some of that tonight because we knew we could cut them open on the counter-attack which we did. On another night we could have been two or three ahead.
"After reorganising the side at half time we then lose two goals but we do well to force an equaliser and from that point I thought we were going to go on and win the game. We kept players up the pitch to force them to keep players back, but we simply do not deal with the ball that comes into the box.
"They need to learn.
"For all that they have played very well at times this year, they are going through a tough spell at the moment, not helped by having a few injuries.
"This is when you look at the players and find out a lot, see who can cope with the test of character and see you wants to stand up and be counted. We will discover that over the next couple of weeks."