Not lost, the interface loaded a comment I had written elsewhere into this thread, which I didn’t even have open and wasn’t reading. When I reloaded the page to try to stop the post it showed the original thread I intended to post to. I had to manually open this thread to see where it posted.
Might pick a few good representative instances on lemmy, mastodon, etc, then make a compound search:
site:lemmy.ml OR site:mastodon.social [thing]
then set up a search keyword like
fs
for it so you could typefs [thing]