Mac App Store - how to check which account was used to buy app
All app downloaded from Mac AppStore(MAS) contain a receipt inside their app bundle (example: appname.app/Contents/_MASReceipt/receipt). MAS will scan this file to check whether the new version is available.

You can use this application (Find Any File) to search any receipt on your drive: http://apps.tempel.org/FindAnyFile/


Launch 'Find Any File' and search for: _MASReceipt
Go through each result that you think could be the culprit, copy the receipt to your
desktop as a backup, and after that delete the receipt inside _MASReceipt folder.
Open MAS and let it scan for software update. If it's still showing the wrong ID, it means that you've deleted the
wrong receipt. Restore the receipt backup from your desktop to
it's previous location.
Repeat the process until you've found the problem receipt.