Hey all, it's been awhile since I posted but I figured I would seek the insight of wiser minds than mine. Best I could find with the search was this, which doesn't really address my situation since I am post-travel:

gift card travel voucher denied after purchase

Here's the TL;DR: 9 months ago, I was duped into obtaining vouchers from someone who may have purchased them from UA fraudulently. Used vouchers for travel completed 7 months ago. Now, airline wants me to pay for the tickets.

FULL STORY
Back in January, I acquired TravelBank credit from another MileagePlus member. I do not know under what circumstances this other person obtained the TravelBank funds, but I acquired them in good faith believing them to be valid. Let's just say that what I believed to be a fair market exchange occurred.

The TravelBank funds were indeed valid, and I used them to book a trip in March. I uneventfully took said trip.

Fast forward to today. I receive an email from a person at "United Corporate Security" reporting that my MP account has been closed, I'm banned from ever flying UA again, and that I owe them the cost of the tickets, or else they will pursue action against me. They claim that the TravelBank credits were originally purchased with an "unauthorized credit card."

At first I thought this was a scam email, but sure enough, my decade+ MP account is closed.

I realize I may need to consult with a lawyer, but I'd love to hear any constructive thoughts. Please refrain from telling me what a fool I am for receiving TravelBank funds from a stranger - that is not what I would consider constructive.

It is my opinion at this time that I am not responsible for the cost of the tickets. To my limited legal knowledge, if B fraudulently purchases property from A and then sells it to C, A does have the right to the property from C if they find out C has it, even if C acquired it in good faith. C would then have to take action against B.

But this isn't physical property. The "item" in question has been materially altered (used) in good faith and no longer has the same value. For example, if C bought lumber from B that he used to build a house, A cannot come to C and make him tear down his house to recover the lumber, nor does A have a claim for monetary compensation against C.

What do you think? Kind of sucks that I lost all the lifetime miles, but I can live with that. Having UA try to trash my credit and sue me is another story.