|You need to do a repair of windows to fix. Tap F11 repeatedly during start up to access recovery system. Do a REPAIR, NOT a factory restore (that one will wipe your drive and reinstall from scratch), the repair should rebuild your boot manager.|
In the future, use sleep if you are going to be away for a few minutes, hibernate if you are going to be away for a few hours at most, and shut down for longer or overnight. You probably just closed the lid and put it into sleep.
You have to be a little bit crazy to keep you from going insane.