First Person Controller (or all scripts?) Not Working Anymore

I searched through the question database and didn't seem to find a question similar to this, but forgive me if I missed it.

I've been using Unity for the past week or so, and everything was fine. Then, without any changes to the demo file, it would suddenly load blank. All the assets were imported on the project tab, but nothing in the hierarchy. What's worse, using the "First Person Controller" prefab in ANY project doesn't seem to work (it doesn't respond to WASD or MouseLook). For that matter, nothing dynamic does -- no animations, no scripts from what I can tell, only laying down models onto the scene.

I've tried moving scripts around in hierarchy, activating/de-activating scripts, re-installing Unity, making sure the scripts weren't modified from their original conditions, all to no avail.

If someone has encountered a situation like this before, please let me know -- I appreciate any help.

I am not totally sure but are you working in island demo scene ? You can build a project with multiple scenes. Scenes are represented by a unity icon and a name (IslandDemo I think) in your project folder. If you go to the project folder and double click your island demo scene it would load the scene ... i hope that you didn't accidentally deleted everything ..!!

what do you do if when downloading for some reason the island demo got deleted?

My problem is that i messed up the script for the movement xD