My sister bought one of those from Armstrongs several years ago. It hatched - zillions of little nymphs. She put some of them in a big cookie container and the rest into her plants. We didn't really have anything to feed them so they started feeding on each other. The outside ones were doing okay until my father watered the plants with a garden hose and we never saw another one after that.
If it had hatched in the store there would be bits of eaten nymphs in the container it came in.
You should have left it alone and just waited the maximum amount of time before cutting it open.