If he's acting perfectly normal then I'd try to calm myself down and keep an eye on him to make sure he hasn't changed. A lot of times the cat would need to ingest large amounts of the plant to have the toxins hurt them.

I know onions are toxic, but my friend's vet told her the cat would have to eat 3 large whole onions for the toxins to kill him. Still... I keep onions out of sight of the cats just in case. Similar here, keep all dangerous plants out of paws' reach or not at all.