Depending on when you actually received the email, this does not prove the passwords are stored in plain text.
I'm pretty sure it's not the case here.
This could have gone like this :
Register, your password is saved in the session, sent by email, encrypted into the database.
If you were to ask for your password and it was sent by email, then there's a problem, otherwise...
Of course sending an email with a plain password is not a very good practice but well...
