Hamun Kost in the Wave Echo Cave?

Hi folks

So my party is about to enter the Wave Echo Cave and start the last chapter of the adventure. They've been to the Old Owl Well and briefly fought Hamun Kost, before he managed to get away and left the party to deal with his zombies.

Just wondering if there's a story where he's in the Cave helping Nezznar? The campaign guide doesn't seem to link them, but they only fought for a turn at the Old Owl Well before he escaped, and have an idea for them to run into him one more time.

Any suggestions?