[My world is just gone!]

I went downstairs to watch tv for an hour, I came back up and logged into the server and boom.  the whole world and seed it different. I spawned in a random location and I have no idea how to get my world back! Me and my friends spent hours on that server and now its gone to waste? If someone could help me get it back, it would mean the world to me

[My World is gone]

This happened to me to just now! This is ridiculous i spent hours opon hours on my server and i shared it with 10 people