Cat won't come out of hiding place or poop - is it OK?

[mdicig]

Hi, All. I am babysitting a cat I do not know and it crawled beneath the stairs shortly after it came (about 40 hours ago) and won't come out. Opening is about 2.5 inches high and very wide - head and front paws get through fine but cat resists too much for me to try pulling it out without undue trauma. I put food and water in there - it's eating, drinking a bit but not pooping. Could it be trapped? It is silent in the day and meows a bit at night, and it's bed is going unused.

Should I be worried?

Thanks!