Motorcycle Repair: overheated, cracked front disc, brake lever, stator

Question
Had my '89 Sporty in the shop for a new clutch and stator.  While in the shop the mechanic noticed the fromt brake needed readjusting.  Bleeder nut needed replacing and brake was readjusted.  Going out for a first ride after the repair, I approached a stop light and dowshifted and braked to slow down.  When I disengaged the clutch and tried to roll up to the stopped traffic, my bike decelerated very fast as if I were braking, but I was not.  Had to re-engage the clutch to get up to the stopped traffic. Once stopped, I saw smoke coming from the brake and the disc was scorched. Brake lever almost impossible to squeeze. Never had brake problems before. Same shop installed new brake pads this past April. Bleeder nut last week.  Hobbled it home with funny noise and found the disc had cracked all the way through.  Brake lever went bake to something resembling normal. Took it back to the shop.

I concerned about getting screwed here.  I didn't do anything to the bike to mess up the brakes.  the only hands on the brakes were the shop's. I just rode it and I have never had problems with the brakes before.  I believe the shop has some responsibility here and I don't want to get buffaloed.

Improprer bleeding and adjustment?

Answer
There is no adjustment to the brake. You have a disk brake and the only thing that needs done is bleed the brake if you get air in the brake line. So I am not sure what they adjusted. If your brake locked up then the puck in the brake caliber locked up and did not release. When they said the adjusted the brake I would need to know what they did, to give you an opinion
Mike