Looks like you got some of your answers, but not all of them. In a nutshell, you got picked up by a dimensional vortex and dropped off here. If you saw something that looked kinda like a tornado? That was the vortex. When you get here, you replace someone. All their IDs change to show your name, your picture, everything. You should check those, they'll help you figure out who you replaced and any related stuff.
There's a website that explains it all. [website] Just to warn you, it's pretty sparkly.