For a moment, I was tossing between two potential events when I read that email. Either someone had gotten into my account and purchased a gift for their own account, or GOG glitched out and thought I made the purchase recently and sent out an outdated receipt for it.
When I saw "remastered" I had to recall if it was remastered originally or if that was some new thing I hadn't heard about.
Seeing this discussion has alleviated my concerns, but wow... they need to sort out how they do upgrade receipts. Don't say I've spent $10 for an upgrade when I haven't spent $10. Not cool, GOG. Sort it out.