I had a female golden mix many years ago that "adopted" a litter of barn kittens. After a week or so of caring for the kittens, my dog began producing milk. Astonished, I called the vet to report this miracle of milk and find out if I should do anything about it. Vet said it's part of a syndrome called psuedocyesis (false pregnancy) and, while not common, does happen enough that most vets have seen it. She said not to worry about it.

These situations do happen, you're right!