HELP! Problems retaining content & layouts b/w sessions.

I prepared a layout, upload content for a meeting back on July 21st,

Then, on July 29th I changed the layout and content and ran a different meeting

Today, when I logged in to update my content from July 29th I found all my changes were gone and the meeting space had reverted BACK to what I had on July 21st instead of having retained my changed made on July 29th.

I lost all my work - why?  When I look at "uploaded content' I can see what I uploaded is there, but for some reason the layout and use of the content did not.

Please advise!