It is hard to say what happened when we don't know anything about your compueter setup, software and what exactly was going on on your computer in last 24h.
But there is only one - in my opinion - way that your installed software disappeared. ou,ve installed AE or other software yesterday, and today on starting up your computer thee was some issue with starting it up. Windows (i gues you are in windows) have a recovery mechanism in witch when you are instaing a news software - windows prepares new recovery point in case something will go wrong. And on today's startup of your system there was some issues with startup so windows operating system found last recovery point (so last before you've installed last softare - in your case AE) and recovered that state.
If that is the case just install AE one more time and check your computer and operatin system because that kind of failed system booting shouldn't happened.
Of course I can be wrong because i don't even know if you are on windows or mac or maby (in some extreme weird way) on Linux but if you are on windows that is probably what happened.