The official website of the developer is down. The only way to recover your password is by using an Email application that you previously configured with your File Hide Expert. If you didn't do this, there is no way you can recover the password.
The application was tested, and a glitch was encountered regarding this problem. If the application was uninstalled and then installed again, the password was removed and all the files that were hide using it weren't lost. You can try this for yourself.