I did. It is one of the rumours that go around, but a bit exaggerated.
Last year I was in Bansko and unfortunately nobody wanted to buy my jeans. About fifteen years ago, not everything was available in regular shops and 'luxury' items as jeans, sunglasses and even condoms were traded on the 'free' market. As far as I know, not anymore.
Hahaha, your info is ancient. Only in communism (15-50 years ago!!!)the stores were empty and people had to buy jeans from foreigners.
But nowadays you can find anything in Bulgaria, so don't you bring merchandise-noone would buy it.