I know it's been brought up before, but shouldn't there be some sort of time limit on obtaining a refund? I would think that you could discover any "mistakes" - duplicate downloads - or improper credit card use within 2 months. The one exception I think should be given no time limit is when you order a larger size of an image you already purchased - there's no possibility for any sort of shenanigans on the buyer's part and allowing a trade-up seems to benefit everyone.
These days most retail stores limit refunds to 90 days. With the simplicity of a digital refund - no trudging to a store required - and no wish to have microstock operate like the Alamy model where you buy now and pay 6 months later, 60 days seems ample to me.
I know that IS and DT no longer wish to explain the reasons for refunds (which I think is completely unacceptable; if you look at any mail order business they have a whole list of refund codes - put one of those into the system and no human intervention is required to be specific about what happened), but don't you ever wonder what on earth made someone seek a very small refund 3.5 months after the fact?
Given that we have a completely opaque accounting system and so far no steps taken to improve it, in spite of repeated requests/suggestions, I'm not holding my breath. However, FWIW the OP's point that if one of the reasons was unauthorized use of a credit card - the company can't control employee use of a card - why are we to be assured that they can control use or abuse in the destruction of the image? And when an image has been floating around a company for over three months, I'd consider a statement that the file hasn't been copied to be just about worthless.