Auto save not saving

Hi,

I thought I was going to like the new auto save instead of manually saving every time, but now not so much. Everything I updated in my spreadsheet the other day is now back to the way it was before I updated it. Even worse is all the NEW data I entered is MISSINGfrom the 9th of April through to the 26th. Just vanished! :( Auto save "saved" it every time, so I can't imagine what happened? Do we still need to "save" manually again before closing the page when we are done using it? I am very leery of entering any further data now. Please help!