I think I just ended up being exposed to the most annoying federation bug

someone boosted a "ph -" post of mine (presumably by accident from the federated timeline), so my instance got told about it, and it ended up in my notifications

this person then undid the boost, as evident from the fact that it's not visible on their outbox - except that was never federated to my instance, so it still says they boosted it in my notifications, and it still says one boost if you open the post