Paid Mechanic With A Check, Bank Says It Went Through, Mechanics Bank Says It Didn't Go Through

My friend paid about 2k for some work to be done on his car. The mechanic shop states that theres a 3% credit card fee, so he paid it with a check. Yesterday, the mechanic called saying the check bounced. My friend verified it with his bank and the bank told him that the check didnt bounce and the money had been taken out already. The mechanic is saying his bank didnt get the money (?) but the car is apparently finished with the work he paid for.

What does someone do in this situation? He's thinking to print out the bank statements to prove it went through, he has a copy of the written check. Is this a common bank error? Does he ask the police to come to the mechanic shop? Should he get a lawyer? How is someone supposed to approach this situation?