Heads up.....Do not deal with this guy

No... Id be pissed too. You are completely correct to share this experience... its not about an error the seller made, the seller made no error... he knew trudy had already paid, so his money was in his pocket.... then sold a walk in customer trudys item to fatten his pocket. What if Trudy had a show that weekend and only purchased from him because he had both in stock? Trudy would be **** out of luck because the seller wanted that extra money?? He should have told the walk in customer, sorry im out of stock, i will have some coming in on such and such date... That is being irresponsible and is a horrible way to do business.
Damn straight. He sold a paid-for part that already belonged to the OP via his purchase. In my little world that's known as "stealing". Maybe I'm weird or something, I dunno...#-o