Not really, I don't think I have a 'one that got away' like that. I think ideas are frankly kind of disposable – if I've pitched something and it didn't go over, I am just going to forget about it because there's going to be a thousand other things pitched and discussed after it. I don't think working creatives tend to get super attached in that way, or at least I don't.
I can generally second this in that if you work on a game for any length of time you're going to have all kinds of ideas from silly and implausible to serious and infeasible and either you learn to move on frequently and love the next idea, and the next, or you become the kind of person that producers resent for constantly holding up the production schedule by clinging onto their babies
I think from the outside it's always easy to think of games as an immaculate construction where any deviation from the Original Ideal is a loss (esp because marketing loves to suggest that they ARE made this way), but they're a lot more like jenga towers that you build all the levels of at the same time and by the end there's probably going to be a bunch of pieces everywhere but it's fine as long as it stands upright
I can't even count the number of "oh that would be cool" ideas I've had in my career that not only came and went, but often went, and went, and went, and went until they were so far from what we were making that they no longer even made sense as a thing that we might want to include
In that sense idk maybe the only ones that truly hurt are the ideas you come up with right at the end, when something is fully formed and it's too late to change it
But you learn to get over that, too. Carry it over into next time.