Let me throw this in the oven and see if it bakes...
I once received a sizable credit on my phone bill. It was not earned, so I called to have it corrected. They thanked me for being honest and I got a warm fuzzy!
Well, that did not last long.
My automatic draft kicked in (paying less than normal for the bill) before the credit was corrected. I then get harassed about having an unpaid bill and threatened with disconnection! It took several phone calls to get it "corrected". So much for their Customer Service records about my good deed!
Ferengi Rule of Acquisition #285: No good deed ever goes unpunished.
My point? Well, it is probably lost somewhere. I think I am cynical enough to think that correcting the Mint's error might backfire.