I apologize in advance for lack of details, and for asking a probably obvious question - mods, please delete if this isn't the right place for this.

My bf just got a replacement iPhone 6 from Verizon as his old one wasn't holding a charge. He's living in a different state, and not very tech savvy, so I only have what he told me to go on. He backed up his old phone to his computer, and apparently while setting up his new phone it said he "had to clear the device and set the new phone to my actual device", so he factory reset his old phone.

Naturally he then realized he doesn't know the password to a single one of his accounts, most importantly his Gmail. And of course he also never set up any backup phone number or email account for it, so he can't reset his password. His old phone was the only place he ever signed into that account (aside from other long-deceased phones), so unless he can somehow get back into the account on there, he's going to lose access to about 8 years worth of emails.

I know this is a massive shot in the dark, but any help/ideas/suggestions would be hugely appreciated.