Thanks for reviewing the case again.
Maybe my explanation isn't clear enough, my point of the "loophole' is, it could create a huge problem to those bot owners that are kind enough to refund, like me and many more. Usually, we do require some sort of screenshots of the trade to prove that the trade actually goes through and the bot did actually take the items with any keys or metal that supposed to be taken. But noticed that, the user, in this case, send me two separate screenshots (https://imgur.com/a/AGyO5Py) through steam making it look like one and that my bot is 'taking' items from the user. Any bot owners that are not careful as I am would most probably be faked by his screenshot, proceeding to send the keys before realizing they are scammed.
The definition of a scam is that 'an illegal plan for making money, especially one that involves tricking people'. In this case, the user was tricking me into that I should give him a refund by sending me fake screenshots/irrelevant screenshots with my bot name and logo. This is very similar to impersonator scam, which scammer impersonate others to trick them giving their items. Only because I did not fall for the scam attempt did not make it not a scam. I understand backpack.tf may not have precedent for banning users who ask for refunds that they are not owed, but I do think this should not be taken into account as every scam method starts from somewhere and I do not think actions should be taken only when people actually fell for the scam.
Any logical person would usually send a complete screenshot and add the 'bot' that accepted the trade, not my bot. I think what happened here is that the user got phished/scammed and try to compensate his lost by contacting me for the refund.
The reason why I think the user 'lost' his item is that to prove that he is the victim of this phishing scam, after seeing the report is closed, he relieves and restores every item back to his backpack again. It makes sense that the user would want to transfer his items away before the day he contacts me as to create confusion and the afraid of getting his account banned. Then, right after the case closed, he transferred all of his 'lost' items back and using them once again.
Edit 1: points to add