It wouldn't be an infinte loop.
Basically you would ask the server from two points all the sells made on a particular item, then have another function/program follow in and find out all the players that are now in debt (spent the money and dont have it anymore). Then you could take each one of those players and check all sells.
Its not that complex. Its just time consuming when you have 10 servers with 2000+ players each. I assume it would take a day or two. You dont need to check every player only those who sold dawn drops on the week of Atomos.
I guess its like in real life, if you ever got stolen money from someone as a part of a deal (even if you didnt know it) - that money would be taken from you.