Are either of you using any third party tools to "clean" your computer? Construct 2 uses the Temp folder while you have a .capx file open, and if some tool tries to "helpfully" clean up all the files in Temp, it just wiped your project. This isn't Construct 2's fault, it's your third party tool at fault for being overzealous at deleting temp files. Anyway, this issue will remain closed until a reliable series of steps to reproduce the problem can be found - there's virtually nothing we can do without that.