I'm posting the lost ferret tips that I've heard here.
 
Two great tips to help them from being lost is opening windows that they
have access to from the top instead of the bottom.  And for doorways to
the outdoors put up a plexiglass barrier (low enough to step over)
between the regular door and screen door.
 
post those flyers everywhere, ferrets can travel miles
 
alert newspaper deliverers, mailmen, etc - people regularly in area,
children too!
 
search areas calling his name and squeaking a toy familiar to him
 
put an extra cage or carrier outside with used bedding and litter in it,
the scent may help him locate home
 
contact vets, animal stores, animal control, etc
 
go to animal shelters in person, may not be aware if a ferret is in
 
check outside vents incase he is trying to reenter home on his own-and
don't use in meantime
 
check dryer tube, a/c - anything with access from outside
 
Make sure he's not in the house.  Make a list of ten places inside that
he couldn't be - then check them.  Make sure he's not stuck behind a
bureau or in something.  Even check places like the dishwasher and
fridge.  Don't empty trash or start laundry without being sure.
[Posted in FML issue 4926]