You really should give some meaningful infos, if you want to get meaningful advice.
Does anyone else has access to your PC?
What happened after your last working session?
What happened before you noticed the loss?
Where has the data been stored?
etc etc etc
It is not unusual that people, who are under stress, sometimes do foolish things when they almost have reached the end of the tunnel... for some reason they can't resist to do some file cleanups, and throw away the relevant files as well.
Debian
