I've been using myibay sniper for many years and never had this happen to me.

Myibay sent an email that I won item # /371017129485 but ebay says that I was out bid.

what went wrong?

This happened because eBay could not provide the final status of the listing after it ended so the sniper assumed you won it since eBay accepted your bid.
Obviously, someone else bid higher so you did not actually win it as eBay confirmed it.

I adjusted the status on your account accordingly. Sorry for confusion.