So I had 20+ Pokemon on my account and today when I tapped on the app, it brought me back to the original screen when you first start playing. My friend who signed up tested using my username when she first started and my username was unavailable, meaning the account still exists. I don't have the password for the account, but I do have the email. So I wanted to know if it was possible to log back into an account?
When you create an account you either have to have a password for your pokemon trainer account, or log in through your google account, which would mean your google username and password. This means you can't start without having a password.
If these options aren't enough, you can probably find a relevant topic or email address to contact Pokemon Go support on their website. https://support.pokemongo.nianticlabs.com/hc/en-us
*on a side note. As long as you can provide Niantic with the info registered to the account they should be able to recover it (i.e. email adress, original user name, etc). But yeah, if you are registered with Google it shouldn't be having problems.