Saving error

I left and rejoined my world because I was noticing some serious entity lag but when I came back I was in a completely different location and had nothing on me. I know the spot I spawned at and it feels like the game combined an old save with a brand new one. Spawning back in I had lost everything on me but when my friend rejoined he still had everything on him. This seems to be a host problem. All blocks weren't changed and chests were normal. This happened during my use of the PureBDcraft texture pack on 128x resolution.