Server Wiped

Me and my friends had made the best survival minecraft server we have aver had, and we logged onto it this afternoon. Everything was fine. About an hour after, we logged on to see everything we worked countless hours on gone. Some things were there, but others were gone. We are assuming that somebody made a server with the same email that we chose for ours. We believe this because the world seems to be a blend of ours and theirs, with parts of theirs showing, and parts of our showing. Some chunks are our world, and some are from a random generation. We are incredibly saddened as we had spent countless hours perfecting everything that we had build, and to see it all gone makes all of us very sad. Please let us know if you can do anything about it. Thanks.

I did not change the version or anything else with the server... any other solutions? We dont havent made any backups...