Scotland moved top of their European Under-21 Championship qualifying group but were forced to settle for a point despite taking a 90th-minute lead through Jordan Rhodes.
Rhodes thought he had completed a memorable second-half comeback in Bulgaria when he added to his earlier header with an excellent finish in the 90th minute.
However, some slack defending from a corner allowed the home side to work the ball through for Georgi Kostadinov to equalise in the third and final minute of injury-time.
Scotland had dominated much of the second half and looked to have given themselves a good chance of rivalling Holland for top spot in Group 10 when Rhodes took his tally in the competition this season to eight, to add to his 40 goals for Huddersfield.
But the goal 20 seconds from time means the Dutch can go three points clear by beating Luxembourg tomorrow night.
Scotland started with a familiar line-up and formation in Lovech with Dundee united pair Johnny Russell and Gary Mackay-Steven flanking Rhodes up front.
Russell had a great chance in the 13th minute when home goalkeeper Stefan Kunchev misjudged a long ball and saw it bounce over his head.
The Dundee United player ran on to the ball and stayed on his feet despite being pulled back by the keeper but he could not get enough power on his left-footed shot as he tried to slide it home before losing the angle and a Bulgarian defender got back to clear off the line.
Rhodes had a curling effort saved by a diving Kunchev after a good take and turn and Scotland were moving the ball abut confidently with Scott Allan at the hub of their creative play.
Mackay-Steven made a good intervention as Bulgaria launched an attack but he lost Georgi Milanov as the midfielder fired Bulgaria ahead in the 33rd minute.
Scotland had numerous players inside their box as Milanov flicked the ball into Aleksandar Tsvetkov but the return pass allowed the midfielder to drive a powerful left-footed effort from 20 yards which just evaded the outstretched hand of Mark Ridgers and finished just inside the goalkeeper's near post.
Scotland took until half-time to recover but they quickly took control of the second half. Liam Kelly saw two long-range efforts deflected over before Kunchev saved his strike at the second attempt after a free-kick.
David Wotherspoon threw himself at Mackay-Steven's driven cross and was inches from connecting in the six-yard box before being booked for his penalty appeals after claiming he was held.
Scotland levelled in the 69th minute after a short corner. Allan rolled the ball to Kelly on the edge of the box and his cross allowed Rhodes to escape his marker and glance home from six yards.
Bulgaria struggled to turn the tide and were caught out with a long ball in the last minute with Rhodes adjusting well to fire home his 48th goal in competitive games this season.
However, Scotland came under injury-time pressure and the visiting defence failed to get a tackle in after a corner as the hosts worked the ball to substitute Kostadinov to net.
Scotland, who remain unbeaten in the group with 10 points from six games, face Luxembourg at home and Austria away in September.
The group winners are guaranteed a place in the play-offs along with the four best runners-up, with the seven winners joining hosts Israel in the 2013 finals.
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