

I have never (and will never) use Threads.
Your instance is federating with threads though, and you seem to have image posts. Maybe Meta managed to figure out that your Facebook and Lemmy accounts are both you and is referring to a Lemmy post of yours federated to Threads?
You can find Lemmy posts on Mastodon, yeah, but only if it’s been federated there.
In regards to Lemmy, there’s two means of federation I’m aware of:
You should then be able to find the post on Mastodon either over the community’s profile, via potential hashtags used in it, or possible the author’s profile if that got federated over too (idk if this happens automatically).
If the post was made by an Mbin user, then there’s also the option to follow the user directly instead of the community the post was made in. Not sure if this also applies to Piefed, but definitely doesn’t for Lemmy.