I had a world that I used when I was on the beta version 1.1.0.9, I left the beta yesterday and today I tried to join another world but accidentally clicked on the beta world, I thought it just wouldnt let me and give me a error message like it always did but no, it actually let me enter the world, because of this a lot of my concrete builds disappeared and I doubt I can get them back when 1.1 releases.

Unrelated comment- The reason I clicked on the wrong world os because of the menu lag bug.