When you say split, how big of a split? How many frames of bees did you put in there? To me a sustainable size is 4 frames (2 brood, one honey, one pollen) and the bees from at least one more frame shaken in. What happens is that all the foragers go back to the original hive, so all you're left with is nurse bees in the split. They'll start flying in a couple of days.