The world hard resetted itself

I hopped into Minecraft expecting to join my world, but guess what, the icon was gray "that shouldn't mean anything right?" nah. My main house and such got completely reset to the day we started this world, but if thats not weird, I still have my stuff, my creeper farm, gold farm, super smelter, and castle all still exist, untouched. to explore, i went through a portal, the portal took me to where my old main nether portal was. I go back. then the ghost portal of doom, takes be back to where to the portal WOULD HAVE BEEN if the game Didn't NUKE ITSELF. also ive never used ANY kind of mods on this world.