When you enter your details on the form in the main page, you won't be asked for which server you are on. You can check this after logging on by going to the user profile page, which is the yellow avatar thing at the menu bar in the front page next to your main active monster.
There is a way to retrieve your
password which is to click on this:
http://www.haypi.mobi/gm/ And go to the tab 'Retrieve Password'.
However, you need to know the user name of the account.
Currently, it's not known to us if there is a way to check which accounts are linked to which devices so you might need to contact support at:
monstersupport@haypi.comto check that. They might not be able to help, however. In which case, you should just try and search your brain for the username, unfortunately.
Good luck!