Digging a mine.

So, I have two Beardies. One is a teeny bit older than the other, by about a month we think. They were gotten as teeny babies back in August. We put together a 65gl living terrarium for them with desert conditions. The substrate is about 3/4 coconut shavings and 1/4 coarse sand. It has worked really well and there is a thriving population of spring tails and isopods in the litter of leaves and random organic junk, with an Elephant-feed succulent, even somebody in there making baby crickets since we see them too. The substrate is approximately 3 inches deep across the terrarium and packed down.
The Beardy we're discussing today is the bigger one, his name is Diggy (Ironically.) Diggy is about 10 inches long now and a fat cow. He/She eats like a horse and I haven't noticed a lack of appetite over the last few days. He had his normal dinner last night and slept in his normal sand pit that he digs in the corner every night (he rarely buries himself and if he does leaves his head exposed. This morning we woke to the normal routeing of basking on his raised branch perch thingy. Breakfast includes a bowl full of fresh kale and he always gets hand fed a few little leaves, same as this morning, nothing was different. About an hour later we were laughing at Diggy's tenacious tunneling as he began digging a hole, at first straight down, then when he hit the glass on the bottom, started digging horizontally. He is now at least a foot away from his original hole, having traversed sideways underground across the tank. His excavation has filled the tunnel in behind him and he's now completely buried and sealed in (his own doin.)
The substrate is pretty dense but I don't have a huge concern about him suffocating, although the worry exists in the back of my head. He's been underground all day. No basking, no movement, missed lunch. Reading up on this, I see he might be prepping to hibernate or if he's really a she, they like to tunnel to lay eggs. But remember he is at most, 5 months old, so I doubt this. Anyway, The Question is, how long should I let him stay down there before mounting a rescue mission and go after him like a toddler trapped in an old well?
Thanks guy's, this is a new behavior for him and we're kinda biting our nails over it.

Did you go in after him eventually?

No... I was waiting for an answer from here.

I'm pretty sure he can get out if he wants to, but what do I know. So I'm reluctant to disturb him if he is starting a hibernation cycle. Also, it's night here now and he'd be sleeping anyway. It's stressful cause I'm not sure if he's hiding cause he sick, or if it's just the time of year. His housemate is enjoying his alone time... Do you think I should go in after him? I'd have to dig up half the terrarium looking for him cause I don't know where he is under there. Once he filled in the hole behind him, there was only one spot along the glass that I could see him in his tunneling, it was about a foot away from his original entry point, but he moved on and that spot is now dark. Haven't seen or heard from him since that sighting. at any time really he could just tunnel up. These guys aren't stupid enough to bury themselves alive and suffocate I hope... Seem like something this lizard would be evolved to cope with. Would really like to know if anyone's Dragon does this when hibernating.

I don't think a lot of people here keep their dragons in loose substrate though, which might be why no one's answered so far. I'd say as long as his substrate is loose enough to allow some form of airflow, it should be fine, but my experience with burrowing reptiles is restricted to snakes. I'd say if he dug himself in there, then there is a good chance he can dig himself back out, unless he somehow got stuck.

Either way, even if he's sleeping, if you're worried, I don't see the harm in digging him out. He might get annoyed with you, but he'll probably just fall back asleep anyways...at least that's what my little one does if I accidentally wake him up if I have to move him while sleeping.

Good luck with your guy though, and I hope someone more experienced can weigh in.

Me too, thanks!

I eventually dug him out. He was fine, sleeping. Bought them a little fake rock with a hiding place under it today, so he doesn't feel he has to dig a hole to get away.