Poor scared baby! Glad he/she's calming down in the crate. There still is a chance there's more, as I don't see much of an end in sight around here. Is your sister keeping an eye open for more kittens, and a possible mom cat? Being that the kitten was so spitty, and hissing, I'd venture a guess that it's feral born, and very thankful to be out of the elements! I find feral kittens turn around quite quickly when they've endured horribly cold weather, and then find themselves in a warm home with all the food they can eat! If the baby is purring, chances are very good you can pat the kitten with your hand, and then slowly scruff it, and do the undertail sex check.