Update from OP: As of Dec 17 (12 calendar days after SWU cleared & segment was flown) - the SWU remains in my account.

So it looks like an anomaly - a glitch in the matrix if you will.

As the (possibly temporary) beneficiary, I think I will wrestle with what's left of my conscience on whether or not to call AA EXP and ask them to kindly deduct the SWU to let me sleep better at night - or - just try to reuse it on another redeye.

But I do have a question - if this is truly a mistake by AA, what is the likelihood that someone else got the shAAft and unknowingly paid for my UG with their SWU? And if that has a high likelihood - is it realistic to expect that if I call AA and bring their AAtention to this matter, would the poor sod be made whole? If both are highly likely, then I will probably do the right thing. If not, then the effort doesn't seem worthwhile.

Thoughts?