I am sure they are fine bro
I have went an ENTIRE month once without seeing the pistol shrimp or yashia goby and then go an entire week and see it every morning when i cut the lights on
They are elusive and very skittish creatures since they are wild caught and not use to aquarium life. But they adapt well and will eat any food offered to them. Pellets,Flake,frozen, you name it they will try to eat it
The pistol shrimp will sometimes venture off without the goby but not far from its burrow due to its limited sight. If you notice their eyes are very very tiny and they dont see that well if at all. And the yashia sometimes you will see it by itself but usually whenever i see my yashia goby, i see the pistol not long afterwards cleaning out the burroW
they usually try to do this at least 2 times a week to 7 times a week seems like. So tell your friend to not be worried or moving around any rocks or anything because that will just aggitate them. and pistol shrimp are somewhat like mantis shrimp. they have been known to pinch a finger in half.