Yeah I had pretty much the same thing happen, I installed a stereo in a old Phaeton for a guy and somebody broke in a stole it. The guy said I did a piss poor job, if I would of done a better job it wouldn't of been stolen took me to court cause I refused to replace it. I took pictures in with me and the judge literally laughed. whoever broke in wanted this so bad they ripped out the fuse box to get at my security starp on the firewall! And the funny thing is it was a $ 75 stereo!lol Did $350 dollars in damage.
I told him he should of gotten an alarm!