The guy took $60 from you for a harness that is, apparently, still sitting in his shop somewhere. Sounds like ******** from the get-go to me.
Local B&M's are going out of business left and right. Its not an expanding industry/field, at least right now. Quite the opposite. You could make a better choice on a career, trust me. So dont let those guys treat you like they are doing YOU a favor. If you are confident in yourself, your skills and your knowledge... act like they are the ones receiving the favor that you are considering working for them. There is a fine line between being compliant, and being their *****. I think the missing wire harness was to find out which you would be to them... and now they know.
Lastly, I bet you told them the same thing you told us, didnt you?... "I tend to lose things alot *sigh*"... instead of saying "who the hell grabbed my wire harness when I turned around???". You set yourself up for this probably.