Ha ha this happens to me so much. I even had to help a poor dude out because his account (and stuff getting delivered) all was under my email.
On a side note, I got the firstnamelastname@gmail, but Gmail often proposed the firstname.lastname@gmail in autocomplete, with my image and all, so I just "recovered" it. Now I have both when I'm trying to ditch Google 🤷🏼♀️