At a friend's place for a Sunday lunch, a couple of mutual acquaintances arrived with an expensive bottle we had taken to their house some months earlier (we were disappointed when they didn't open it). Our lunch host was very appreciative – the wine was great – but the couple did not acknowledge it had actually come from us. I felt like saying something to them.
Re-gifting is a kind of extreme sport for the sedentary and thrifty. Like base jumping, it is shrouded by taboo, fraught with peril and potentially catastrophic. Success hinges on subterfuge and planning.
Your acquaintances observed three of the essentials of successful re-gifting: they passed on something their recipient liked; the item could plausibly have been purchased especially for him; and it wasn't something he had previously given them. But by failing to foresee that you might be there, they crashed and burned.
Or did they? Whether or not you agree with it, passing on gift bottles of wine is a reasonably common practice. You did not say anything at the time. It is possible the couple in question did not realise or remember that the bottle originally came from you. They may have grabbed the first thing on their wine rack on their way out the door, and remain blithely oblivious to their re-gifting faux pas. Or perhaps they did remember and high-fived each other on the way home – mission accomplished! They mustn't have remembered they gave us that bottle, they didn't even mention it!
It would have been easier had you come straight out and said, with genuine or confected delight: "Ah, the Fancypants Estate pinot! Thanks for bringing that, we didn't get around to opening it at your place, did we?" That way the host would have understood the wine was originally your choice, the re-gifters would have had a graceful out ("we thought you were coming today, that's why we brought it") and you would not now be afflicted with chagrin.
If you really don't want people to pass on a bottle you've given them, inscribe a personal greeting on the label. Just be aware that doing so often signals to the recipients they're expected to put it away in their cellar instead of pouring it for you pronto.