Maybe the buyer knew something?

Yes, it happens, the buyer has their email set so tight that anything not coming from someone in their address book, gets shunted over to spam. Then they forget to look and hit the delet all because there were 128 spam messages.

Use the link that Julie suggested and you should be able to get the buyers address and maybe more.

Last time I had a non-responsive buyer (after emails and multiple invoices) I waited until the last day and posted a Neutral on them as bid on auctions and never paid. If I was only a little bit meaner I might have thought negative but it was for two postcards, so it wasn't really important.

No way for Negatives in return because the time was up.