It's pretty normal for them to explore the first day, and then hide for a week or two after that. He'll start poking his head out again when he gets really comfy and settled in and maybe a bit more hungry. They're most active in the evenings---my babies and juveniles come out around dinner time. My adults hide until I turn the lights out, and then they spend the next hour or two bumping around while I'm trying to go to sleep.

If that f/t mouse was actually warm to the touch, then he's just not hungry yet. Try again in 5 days, and then again in 10 days. If he won't eat then, let us know.

14 inches is pretty young. He's a 2011, but how old exactly depends on how often he was being fed.

Welcome! And have fun with your new pet (when he finally gets settled in).