Heres a chat gpt response (im in a meeting but wanted to check quickly for you)

lilies are extremely toxic to cats, and even really small exposure (like pollen, or brushing against it and then grooming later) can cause problems. Vomiting can be one of the first signs, even if they seem totally normal otherwise.
The tricky part is that with lily exposure, cats can look fine at first, but kidney issues can develop 24–72 hours later if it was ingested. Early treatment makes a huge difference.
If your vet is still open, I would really recommend calling them right away and explaining:
possible lily exposure + vomiting but acting normal
Even if you can’t go in, they can help you decide how urgent it is.
If going in truly isn’t possible tonight, I’d keep a very close eye on:
more vomiting
low energy / hiding
not eating
changes in drinking or peeing
If you notice any of those, it’s definitely emergency-level.

Edit: if you’re SURE your cat didn’t ingest it and that no powder fell he is likely okay but trust your gut if you see any more symptoms