Warning - Editing Multiple Stores
The same thing happened to me a month or so ago. I only have one account and only basic shops, unlike the person who posted, but the situation was basically the same.
Here is what happened to me. I had one window open writing the front page description of a shop. I wanted to see what description I used in another shop and opened the manager for that other shop in another window. I went to the manager of the other shop, opened the window with the front page description and read what I had written there. Without closing the window of the second shop I went back to the first shop, finished writing the description and saved the information. The next time I checked the second shop had exactly the same description as the first shop, even though I never edited or saved anything new in that second shop.
You see, what happens is that if you have two windows open with shop manager edit pages of two different stores in each, when you save information in one shop it will automatically be saved in the other one, too.
I only had to rewrite one description, but I can imagine how much of a mess would it be if the layout or descriptions of a premium shop would be overwritten and gone.
The moral of the story... Only edit one shop at a time and don't even think of opening the manager of a second shop until you finish working on the first shop.