I would advise any new ferreter to fit a locater collar on each ferret they are going to enter, that way you stand a good chance of getting all your ferrets back.
However there is another method and that is to use 1 collar on one ferret.That ferret would be the one which would have been the line ferret,usually a strong unsociable hob that will find and stay with the kill until dug to.
Hobs like that in my opinion are like rocking horse sh*t,you are more likely to lose him than any other, ie collar stops working goes to deep.
The line is only any good if you have the ferret to go with it.I