I've had a few of those today where I get an 'Item Sold' mail from Guild Store but there's no gold attached. The only option given for the mail is 'Delete'.
Is this a bug? These are new mail too so they've never been opened before.
I Have numerous items up for sale spread over 4 guild stores. It would be tough to tell which sold and which didn't. And the generic mail from the guild store doesn't help. So many times something got sold and I have no idea what it was - not even a message indicating which store it was sold from.