Thanks for your reply. I'm still really worried about the issue. I didn't have Bluetooth enabled & was in my home, but that's a point worth remembering for the future too.

I have the other eBayer's user name & email address and have sent them a message to let them know of the breach. I fear that they'll write it off as spam & ignore it.

I'm really surprised that eBay didn't take this more seriously as it's a pretty shocking security issue. I had full access to the user's ability to purchase, message, or amend orders. 

And I have never experienced this before either & have been with eBay for well over a decade.