Well it's about my B.Tech project.
I had windows 7 and I had lots of imp data along with my project and I hadn't taken any backup of my project(not even report copy). So after successful completion of my project I thought let's play with OS and try other OS and that time I had rare awareness about data and OS too.

So I had copied my imp data(mainly friends party pics) into my friend's external HDD and I thought yeah I have clean chit now and literally I forgot about my project which was in C:/ drive.

So happily I had done experiments and enjoyed a lot and one day my my project partner asked about project copy and I had just given a smile.
RIP.
Happy Ending :D