Who did this - something's been chewing
 

This is an Aliceara, growing well, flowering regularly. I just turned it around and found the leaf damage show in the pics (first pic is the back of the damaged area). The damage is confined to mostly one leaf, with little on two others. I don't know when this happened.

There's no obvious signs of pests on leaves or the potting medium. There are no flying pests that I've noticed.

Look for crickets, cockroaches and slugs/snails. Slugs/snails are less likely because most of them eat in from the edge.