I would also give it a bit longer - they are very scared, so will take a while to calm down. Can the lady put a "Talk Radio" station on whenever she is not in there talking to them herself, to get them relaxed around human voices.

I don't know if I would force the petting just yet. I tried that with Ginger once and he practically did a "spiderman"straight up a wall to get away from me.

If there is food and water I am sure the hidden one will come out eventually. Maybe your friend could tempt them with a yummy treat like some tuna or baby food?