I like bhatnasx' idea. But the original FTer's intent in making the gift was that I use it for its intended purpose, which I have done. Ultimately, I've concluded that Thumper has expressed my thoughts most concisely. I had posted the question for two reasons, the first of which was seeking precisely the clarity that Thumper provides above.

I don't know enough about Buddhism to be sure of this, but if it's worth its standing as a major religion/philosophy, I suspect Buddhists would say it's an improper application of the principle of karma to advocate cheating someone because I've been cheated. That was never my intention or motivation, but the discussion of that aspect has helped me see the situation clearly.

The other purpose in posting the question was to find out if there were important considerations I was missing. And it turns out there was at least one. I had not considered the possibility that the coupon provider might prefer that it be used again in order to promote business they might not otherwise receive. So I may call the coupon provider and find out their thoughts about it. However, they don't just leave these coupons out for anyone to take, so I doubt they'll want it to be reused.

And while I disagree with most of what Marathon Man says above, the interesting twist is that the coupon is a Starwood coupon. So even MM is arguing that it should not be reused.

All in all, it's a lot of wind to blow about a pretty insignificant monetary value, but if we're unfaithful in the little things, there's no hope for the big ones.

I appreciate the input from everyone, and I hope the discussion has been of some value to others besides just me.