Setup a camera to record the door(s) for a few hours...leave a few leaves on the floor outside the doors too.
If the cat did do it then the leaves will be gone or shredded and the video will have all the evidence you need.
Cats love tender young leaves. The healthier the plant, the more tempting it becomes.
My asshole cat ate a few seedlings not long ago. Needless to say, we didn't speak for few days.
Then the neighbors cat dropped this on my camp floor last week. *Scroll down at your own risk*
Oh, its the cat alright.
See the older large fan leaves with the slash like puncture holes? That's the cat testing the leaf. You can see in the pic where kitty moved on to some younger ones. They kinda go in side ways and gnaw at an angle using their back teeth. They gnaw them right down to the petiole.
I'm embarrassed to say just how familiar I am with that damage.