Aestavation?

[John]

Well he's been underground now for a full week so he hasn't eaten since then. He was eating well before though. Just before he went under, he pooped and ate 5 nightcrawlers.

Then I wouldn't worry.

[T0ADMAN]

It's been awhile since I've had a pacman, but I remember they do like to dig from time to time. If you hear him trying to dig further he isn't aestivating. They can form a membrane and go dormant if you keep them too dry. Once you get them wet again, they'll come out and be active again. But, like John said if he's moving and eating well, I wouldn't be too concerned.

Is he in a high traffic area in your house? Anything new that would scare him? How long have you had him, and is this the first you've seen this behavior?
Often if frogs/toads hide, it's because there is too much activity near their cage. Most aren't very social creatures.

[TypingMonkey]

I've had him for 4 months now and it's the first time I've seen this behaviour. He's in my room the only person he sees is me coming in. He has already associated me with food though because he sometimes charges at me and opens his mouth when he sees me come in. Usually he would hide then when he gets hungry he would stay out in the open until he eats then he goes hide again.