You really didn't need to post in every other section of the site to get people to come read this. We all go through the unread posts, and would see it.

Cash is for transactions made in person. paypal, money order, cheque are for mailed/internet transactions. It's illegal to mail cash for a reason.

You got the parts? don't resend the money. See if they post up on here that you are ripping them off....if not, you know they got the money..... did you mail the cash to the same address as the return address on the parts package you got? It's rather rare for mail to get lost.