Minecraft has crashed, destroying all my things

"Minecraft has stopped running because it encountered a problem; Ticking memory connection"

When I reopened the game, I was suffocating inside a rock block (y=73,000 feet pos; x=-217,53937). I was inside my mountain home before the problem. I can hear the "laundry machine sound" of the Nether Portal, but it's difficult to be free. When I got off the undergroud, I saw that my home chunck was replaced by another. Inclusive, the biome was changed. My home was completed lost, with all my items. Fortunately, I backed up the game before playing, so I lost "only" the 3 hours of today, not the complete playing time.

I attached screenshots showing how did the place was and how it got to be after the crash.