I’ve had it happen to me once - more specifically, it was one of those situations where you make a clever meme but then find it reposted in two different places (or four different social media, in my case), both with more upvotes than your own post AND without getting any credit.
It’s a mixed feeling:
pride, because many people thought that the meme was worth spreading (especially so if it’s a meme on a niche topic);
understanding, because it’s not like I credited the artist behind the template;
envy, because… y’know, no street cred for me.
[here] if you don’t want to leave the fediverse, but the original is on Reddit (unless they banned me without me noticing, it’s been a while since I bothered with the Bad Place)