It usual takes several things to get a total infestation like your worrying about. Most people's pets have fleas for weeks to months before they discover them, enough for the fleas to drop and get all over.
One good thing about them (if there is anything good) they don't tend to spread out like most insects. They do search for the best most opportune areas once matured to hitch a ride for their meals and are rarely caught in kitchen cupboards, closets (unless your pet hangs there) etc, they are attracted to areas where pets and people stays in that area frequently and they tend to congregate where pets seep, eat, play etc, rarely in rooms where the dog never goes, with the exception of jumping off a pet, occasional they go flying in areas pets don't usually populate. The eggs do drop everywhere and when hatched the large hide deep in carpets or under furniture because they don't like bright direct light. When it's bad enough to have an infection like your worrying about it's been months and months where they have been breeding and living unchecked. By then they are everywhere, in the furniture, on counters, behind and under warm and darker areas and especially eating on your pet.
Seeing that the kitten was there less than 3 days chances are with what you have done and what your planning on doing, that should cover it well. The several infestations I have helped destroy I vacuumed daily and used flea powder / spray weekly, they were sufficient enough to kill off every pest. Unlike roaches that live on anything and live everywhere whereas fleas need a blood source to survive, they congregate where they get their food and don't disappear to make giant nests like roaches or ants. Their total survival depends on a warm blooded hoast, does not make sense to congregate in the bathroom for instance and wait there hoping something may come soon before they die.
A fleas life style pretty much consistes of birth, finding a host to feed on, maturing, mating, eating, laying eggs and repeating the eating and reproduction till they die. They average about 3 month life span, the females do not start laying eggs until her first blood meal. She eats lays eggs, when the eggs are mature they drop onto the carpet and dig deep into the carpet or under furniture away from the light unti they hatch. Once they hatch and are able they jump onto a host to feed and the cycle keeps going.
Breaking the cycle consists of using flea products, daily vacuuming as well as washing the pets blankets and bedding weekly, and shaking them out daily outside away from the house where your pets don't hang out and hanging them in the bright sunlight outside. Most people recommend twice weekly for washing and then line drying. You can use a hot dreyer if the fabric tolerates heat, most pet beds don't because of shrinkage.
From the short time the kitten was there chances are you won't have an infestation if you've cleaned and vacuumed well. Many people say vacuuming weekley is enough but since the eggs hatch daily I vacuume daily because twice a week I didn't see any dent in the enormous problem my brothers house had, once I started daily then they seemed to disappear at a fast rate, after 5 days we could no longer see them jumping around on the pets bed. After a week we no longer found any hiding, however we kept up a solid 2 week assult just to make extra sure and won the war against them.
Good luck and don't worry so much, without a host they cannot reproduce.