Apple ID has been changed after reset

I was planning to give my old iPhone 5 to my mom as her back up phone. I proceed with the reset process. I entered my code and my Apple ID and it went through just fine. I also received an email that my FindMyDevice has been disabled while the reset is on going.

In the set up page, it is asking for an email that was used when setting up the phone which is a Yahoo email address. I have never used a Yahoo email address and my Apple ID is GMail. This is confusing because how was I able to reset my phone if my Apple ID is incorrect? Has there been an incident like this where an Apple ID was changed after reset? Thank you team!