Sudden Crash and loss of saved data

[Alcy]

I have created a few substacks of my main stack.
I have been working on a very heavy substack (with about 700 buttons 
with different scripts) for the last 2 days when a script has generated 
a crash of revolution and surprisingly when I have reopened the stack, 
all infos about the substack had disappeared. It is not the first time I 
have a surprise like this. I have saved my work under another name too 
but the same thing has happened to it as well (no substack)..
Has this phenomenon happened to others?  Should I save each substack 
separately?
Any idea about why my saved data have lost the infos about this heavy 
substack?
thanks in advance.
Alcy