1997 Chevrolet Cavalier Horn does not work

An auto mechanic installed a new horn. It worked once installed, then stopped working. It went back to the mechanic, he said it was a ground wire, and he replaced some wires. The horn worked that day, then stopped working. It has not worked for 5 days. I am hesitating bringing the car back to the same mechanic. What is happening with the horn?

Thanks,
Eric