Lost some bees

I discovered one of the three hives that survived the winter and the first one I put supers on had left. Completely cleaned out except for a few SHB and some wax moths. So I guessed it swarmed and I missed it and then pests invaded. Guess it must have happened a couple of weeks ago. After putting supers on I had not checked inside the hive. Always activity on landing board and there were a few hundred bees - but only open comb. Guess I will start a nuc.