Regardless of what you thought your bed time should be, and regardless of what your actual mental age was... Your body still had hard physical limitations. It wasn't long before you were out like a night.
In your sleep you completely forgot about the Age-O-Matic. Mark however did not. With you safely in bed he headed back downstairs curious about what the strange gadget he had seen you playing with was earlier. He assumed it must have been some kind of game and picked it up trying to figure out what it did. He saw each of the settings you had it on, but he didn't quite immediately believe it would actually change someone's age.
Being asleep in your bed you had no way to warn or to stop him... Instead you could only wake up to see the day day. Then the next morning...