I have no idea why this happened, but yesterday I opened my VV3 game after leaving it paused for 48 hours. When I opened it, all of my building progress was gone. The leaves were no longer cleared from the roster of the dead, the lift was broken again, the bath was back to NOT being restored, the 2 keys I had (pink & white) were no longer in the door, the alchemy lab was in ruins again, the orchard was gone, the sharks were back to being dangerous, and my huts were all broken again. My puzzles were all unsolved again. I still had all of my awards, food, collections, technologies, people, and tombstones. Also, my fire was out.

SO FRUSTRATING! Any idea why this has happened? Has this ever happened to anyone else? Other than redoing everything, any idea what I can do?

My guess would be that something like a power outage or a change to your system clock corrupted your game files. You can try to restore your game using the saved game files, but unless you created a backup it may be too late.
Here is a post by LadyCFII that better explains how to make backup files.

This FAQ answer may help you. Alternately, there's a post here that has a similar situation.

Thank you so much for your help. I searched the posts but didn't find the ones you referenced. It's too bad I have to redo everything but at least I can back it up so if it happens again I can fix it.

Thanks.

You are very welcome