Dont give up hope . One of ours was missing for over 2 days . We looked everywhere , searched peoples gardens and everything , put posters on all the local lamposts etc, and lo and behold , got 2 kids call at the house on the third day saying there was a ferret playing with a paper bag on a pavement only about 150 m from the house! She was none the worse for it thank goodness . Good luck to your friend, the remaining ferret will be really upset and lonely without its friend - they are SO sociable and playful so I hope it turns up soon.