Okay, if some of the others eggs hatched before the other eggs the tiny caterpillar has a bad habit of wanting another yummy egg snack. They will crawl over and egg another caterpillar inside of its egg.
Sorry. Their eye sight is very bad.
Then, there's the tiny hiding spiders, assasin bugs, and other predators.
Check the under sides of the leaves, for predators. I usually wash the plant off before I enclose them, spiders hate water. Caterpillars also like to play hide-n-seek. Most of the time you will find them hiding under the leaves or at the very top of the plant. They may show up later.
In the future, when hatching eggs make sure you separate the newly hatched caterpillar away from his egg brothers/sisters.