You have learned a valueable lesson today: always make daily backup copies
of important work.
Whenever I am working on stuff that is important, I zip the whole folder,
add the date to the filename and
copy it somewhere safe, like a network disk or a USB key. If possible I do
both to have redundant backup.

And in the days of the floppy, I used to check if I could unzip the backup
file as well.

That way I only lose a day's work at max, no matter what happens.