How to report a member for not delivering the part but taking my money?

I have ordered parts from dozens and dozens of members from all of the different "Bodies" forums over the years with success and I thank you all for that..... The one thing I have noticed it sometimes takes days to weeks longer for payments to arrive and parts to arrive back.
It seems all of the sources. Especially, USPS. Even UPS and FED EX are even taking longer these days. One just needs to be more patient.
I had one transaction from Penn to Mi took 4 weeks and 4 days to arrive. It kept getting stuck in one terminal for days, then another for days.

I've had a few purchases from this site and they were all trouble free. The first purchase was the actual car, felt like I was gambling but it paid off. Hell I specifically joined this forum to watch the for sale section, if I joined sooner maybe I could have talked KD out of Jigsaw before he went and made it all valuable