First of all, if you want any kind of item recovery, you need proof. Nothing can be done without it.
Second, players can change rules. I know people sometimes miss it because they aren't paying attention, but we have a second screen for that.
He did not hack, he simply changed the rules and you accepted. This is all fair and square. Please pay more attention next time.

Locked.

EDIT: Send in a ticket here next time. Bug reports is not the right place to post anything like this.