1995 Ford Escort Brakes

I recently brought my car in to fix the brakes.
The shoes, pads, rotors and calipers were replaced on both sides of the front brakes.
Since the brakes have been fixed, the caliper mount bolts on the driver side have fallen out twice.
Both times I went back, and they "fixed" the problem, explaining that it was probably a manufacturer's defect on the parts.
One of the bolts has fallen out a third time, and the second is loose.
I'm thinking that this is shoddy work on the mechanic's part, but am not sure how to proceed to fix the problem.

Thanks