What could be the cause of clunk sound from front end of my car?

I have a 2002 Chevy Cavalier. I noticed the sound seemed to start about 3 days ago. It happens when I shift into reverse and sometimes while turning a corner. It doesn't happen every time I shift into reverse or turn corners. My friend thought she could feel something move under her feet on the passenger side when the noise occurred. I took to repair shop and they put my car up and looked underneath. They said the bushings were bad and thought that would fix the clunk. When I got the car back I put in reverse to leave and there was no clunk, but next time I used the car and put it in reverse I heard the clunk. Any suggestions on what it might be and possible cost to repair? I plan to take back but would like ideas what it might be. (This may have nothing to do with the problem, but couple months ago I had to have my car towed from my garage because lock cylinder went bad. They couldn't get car out of gear so they hooked a chain underneath the back of the car and dragged it out of the garage.) Thanks for your help.