fleas on sheets?

I recently sprayed my whole house for fleas and have still seen a few around and some eggs on the carpets. We plan on replacing the older carpets and I think I'm just going to bomb the house if I can find it.

Last night there were fleas in our sheets which were just put on the bed a couple days ago. They were hung outside to dry the last time I washed them could they have come from outside? Or maybe they were in the linen closet?

Have the cats been treated with flea treatment prescribed from the vet?