How old is your RF? You say he is tiny, does that mean he is a hatchling? Their tendencies are to pretty much hide most of the time. I have two RFs (4 yrs old and 4 months old) and the youngest generally sleeps a lot or hides out in her cave. She does bask (or I'll catch her basking).

As long as he is eating all right and growing at a good rate (no pyramiding), I wouldn't worry about it. He'll "come out of his shell" in time.