Sometimes snakes recover from minor RI's with a little more warmth, so to encourage him to use his "warm hides" you might try filling it with damp sphagnum moss.
Garden centers & florists carry it, besides pet stores: soak it thoroughly, then drain out most of the water before installing it. I bet you'll find him in there, & of course,
you'll have to keep misting it (or re-soaking it when he comes out).
Another possibility is that he has old stuck shed (especially in his nostrils) from insufficient humidity...and damp moss/raising his humidity can fix that too. I love corn
snakes, I hope you do well with him. Previous owner (or store?) may have kept him way too warm &/or dry. I hope this is an easy fix...and I definitely wouldn't rush to
a vet before you find out if symptoms are from an incomplete shed. Now if you see his mouth bubbling or with mucous, that pretty well identifies an RI, but try this ^ ^
first.
I would put the wet moss in the cork-bark hide...that will help catch the drips. Make sure it's very cozy & best to block in* one end of it too...open tunnels
(or hides with such huge "doorways") don't offer a feeling of security to a snake. *You can use something temporary like a piece of clean cloth over it if you
want (so you can peek in now & then too). As a yearling I'm sure he's seen people before, but being in a new home is still very frightening to a snake and
stress takes away from the proper function of their immune system, much as it does ours.