if he pulled a live wire loose and it grounded out somewhere it could've melted the wires together... that's what happened with my jimmy.. somehow the cig lighter + wire came loose, grounded out, heated up real bad, and all the wires behind the radio melted together causing a ton of trouble one of the many things that went wrong in that truck.

Good luck. Doesn't sound like there's going to be an easy fix for this one.