A player setback glitch going on...

So I have been doing stuff irl for around 5 hours, and grinding on minecraft, letting the mobs spawn. Well, after a while I check and a teammate has betrayed me. As you can imagine im pretty mad, but oh well. Suddenly, i lag out, and back in automatically. Im around 2 hours back, with all my stuff again. But, the stuff Id done to the map before going back was still there. Server is 1.3.2 vanilla. Any ideas? Im not the only one this has been happening to on our server.