I am so sorry. Do you know what type of mange it was?

There are different types of mange, some are contagious.
Sarcoptic mange is the same as scabies in humans and yes it is contagious & can be transmitted to humans from dogs & vice-versa.
Sarcoptic mange is something that any dog can get. Foxes are natorious for spreding mange, so say a dog runs through a field, rubs against a brush that a magey fox ran into & your dog can get it. A dog can even goe to a park where another dog had mange has been and can get it that way. Its a pain but something that can be treated and something that may not be avoided. It is not the pups fault & may not even be the forster moms fault.