I just summoned Bonemass for the first time, and have travelled back and forward to the swamp since a couple of times, and each time I get the green screen with the rain and he appears again, but when I go back now, he's nowhere to be found. Does that ever happen? Or does he have to be somewhere in the swamp, it's just a case of finding him? Just want to check before I use the console commands to spawn him if he has disappeared - I'm not hunting for withered bones again when he should still be around!

EDIT: thanks for the responses everyone. I didn't even think to look in the trees 😆 instead I just used the console to respawn him 🙂