1.> In top right corner, click members
2.> Click "toggle more options..."
3.> Type in the member's name in the box under where it says "Signature Contains" and press enter
4.> If that member's name is in anybody's signature, the users with that name in their signature will pop up and you can contact that member to find out how the sale went. Also you can click the member's names who come up in search to see their profile and see what is in their sig about that member before you contact them.
Please note, not all members might be in someone sig, so don't get upset because you can't find them.
Addition by Grim187:
one thing i like to do before sending paypal payment to anyone is check to see if there paypal account is verified, you can do this by adding there email address at the end of this link (replacing the "@" sign with "%40")
i.e. if you wanted to check if "Someone@Something.net" was Paypal Verified the link would be
note: you have to have a paypal account and be logged in to view the page.