Problem of automatic deletion of data from database MVC4 RAZ

Question

Hello everyone,
I am currently in the process of creating a web application in asp.net mvc 4 razor.
I have 3 tables linked by a join One to One.
This afternoon, I was working on, and after having had an error (for data management of my tables by a user), I found that my database is empty. In y'avais nothing like data. But 5 minutes before it was full.
Do you have an idea of the problem please ???
I do not want that to happen at the completion of a major project.