He probably decided to stay in to gnaw on/guard his carrot
Hope he comes out as normal again soon. Just keep an eye and make sure he seems well. I put a little bit of substrate on top of our Syrian's wheel each night before I go to bed then I can see if he's been on it during the night (ie substrate gone). As long as he's using his wheel and taking the veg I put out each evening, I reckon he's ok - but obviously you need to have a peek at them as well to see they look well enough.