They can be odd individuals, can't they? Taking time out of the water is normal. The "rule" is approx 12 hours out, though I've seen some of mine stay out for days at a time.
They are nocturnal, so possibly it goes in for a dip at night and then returns to the air when you're around and noticing it more.
I have one that disappeared into a back corner as soon as it was introduced into the tank; I searched for a month and never found it. Assumed it was dead. Then, a deep vac unearthed it and it began to move slowly and eat slowly as though it had been in a coma for that month. Eventually it made up for lost time, and now it's a hefty eater and one of the bigger guys.
It's still alive and one can only assume it knows where the water is
so I would watch and see what happens