I bought an item 16 days ago, it hasn't arrived, although the seller page says it has been sent. I bought it as a guest. I cannot find anyway to contact e bay or the seller and I have no idea of what name I used as a guest

[ I have tried all of the obvious ways to contact both e bay and the seller several times , and just go round and round in circles]. It was a cheap item so I'm not that concerned about the money, but it is very annoying to be treated as a fool: this will be my last time I deal with e bay.