A neighbor asked me to log her Facebook account with email address firstname.lastname@example.org, which turns out to be inaccessible or non-existent. With so many failure attempts, I decided to assist her creating an account by starting to create an email account. See screenshot of Yahoo welcome message below as proof that it was created today (Feb. 24, 2015). After creating her email account, it's time to proceed to Facebook.
Second step: Facebook sign-up. By filling-up the sign-up form using the newly created email address, Facebook prompted a message "claim this email option", it turns out the email is associated to Joanna Arigo, with Facebook url (https://www.facebook.com/joanna.arigo), the bug or problem? That's what I'm not sure of. Probably, Yahoo deactivated Joanna Arigo's email address while Facebook still keeps it Joanna account settings.
With a few tries, we were able to access Joanna Arigo's Facebook account via verification. This has to be investigated by Facebook, I would consider this an account creation bug.
Since Joan (our neighbor) was so desperate to own a Facebook account, I suggested her to create using her mobile number. Now she have this account, Joan Arigo with url https://www.facebook.com/joanarigo25. It could have been the best option from the start though.
Take note, these individuals have no actual connections although they both have the same last name. Based on Joanna's friends, she appears to be living in Visayas (the central part of Philippines) while Joan is in Mindanao (Southern-most part of Philippines).
Since Joan obtained the account of Joanna, she now have the option to abuse the account probably due to the email account association. This could happen again to any Facebook user, so I hope this could be resolved the soonest.