Most folks will have experienced "the one that got away", be it a particular locomotive, rolling stock, accessory, etc. For one reason or another, we had the opportunity to acquire the prize but just missed out. Whether it's being sniped on ebay, not going to a swap meet you'd ordinarily go to but didn't only to discover that the piece you've been looking for was there at a reasonable price and you missed it; worse, nobody remembers who the seller was, or if they do, by the time you contact him he's already sold the piece. Worse still, you may still be looking for it. For one reason or another, that piece you most wanted to acquire, eluded you.
In my "one that got away" story, the piece was a large door 2530 PW baggage car. They were very hard to come by, and the very, very few that were available carried staggeringly high prices. Well, I attended a very modest TCA meet about 15+ years ago and was walking an aisle just after the show had opened when I spotted the piece on a pretty non-descript table of trains. I was right behind a fella--couldn't have been more than 3' behind him--and he reaches out and picks up the piece. I bide my time hoping/praying he'll put it back down on the table. Of course, he didn't. He paid the seller a modest amount (I want to say $100) and he moved on. I was mentally shot having come so close--literally within feet of that 2530 large door baggage car--only not to get it.
To this day, I have not seen another. Still want one; and I'm still looking.
So, share your "one that got away" story--we all have them.