Lost all stuff and Xp

I went to the server when this "internal exception java.io.ioexception connection reset by peer" popped up. I tried joining again and the same thing happened. I then went to google and searched how to fix it. Then I saw that someone had the same problem as me and they said to delete all the player files. I then proceeded to do that. It worked but all my op stuff and Xp were gone....