Don't worry, you still have your Youngs.
You probably created a new account by pressing the "Google Login" button or by manually creating a new account.
To recover your original account, try to check which email address Stepdrop emails arrive at and use that address, eventually by following the "forgot your password" procedure.
If you still can't log in and can't remember how to log in, write to email@example.com
specifying your username and the emails you could have used.