pahoo......
tell your friend to either feed the ferrets before he takes them out then they are less likely to kill and sleep down the hole....
or tie a long piece of string around the ferret so he can pull it back out if needs be..
or there are great ferret locators on the market now so he could dig him out and grab all the rabbits in the stop ends at the same time...
but to be honest with you the ferrets are not trained right if they dont come out when called..