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I am sorry Mac is hiding.
It is normal for a scared kitty to seek a "safe" spot where he feels secure until the "danger" passes.
As long as he is eating and using his litter I would not force him out. BUT when he comes to the edge try to coax him out with tuna or other food he cannot resist.
When you get him feel all over his body and look in his mouth for a stuck item or any abnormalities.
If possible. close the door and spend some time in there with him.
He trusts you because you are his "mommy" he will feel safe if you are in the room.
Get a felway plug-in. It goes into an outlet like glade and is calming to cats.
Try to pet and sooth him when he is out. Use a feather wand to engage him in play.
There is an item called a thunder shirt that was invented for dogs but can calm cats too.
Here is a video:
You can also try wrapping him in a blanket to make him feel secure.
Please let me know what happens.
Warmest best wishes,