Re: Found a kitten today...
What I would do: If I see a kitten alone anywhere...I am taking it home to care for. Especially if Mamma is a feral, I want the opportunity to raise and socialize the kittens so *they* can get good homes and if I can, I TNR (trap, neuter, release) the mother cat.
I would bottle raise the kitten with KMR (kitten milk replacer) and a bottle/nipple. I like the PetAg brand bottles/nipples and I like the kmr product called "Just Born w/ Colostrum" made by Farnam. If it is only one kitten, I use the little pre-mixed cartons. If it is a litter of kittens more than 2, I buy the canister of powder and mix it myself, making a fresh batch every 24hrs.
*the reason why I do this, is I want the chance for the kitten to get a good home. If Mamma was moving her nest, either one-at-a-time and dropped the kitten, or was moving them all together as a "field trip" and he got left behind, I would say an hour is plenty time to wait. I would never wait overnight, and certainly more than a few hours. The cries of the kitten...if they don't attract Mamma...will eventually attract the attention of *other* animals. Animals that could harm/kill the kitten.