is my account.. gone?

this pains me so deeply to ask... i havent played in years, but bought the complete version in the hopes of continuing. i marked how i logged in (and didnt have issues ever actually logging in) however.. it was through facebook.. i used the facebook login option, and now i dont see a way to transfer/connect that to a nintendo account even on the original app. is that feature just removed entirely, thus my account is gone?! i did e-mail nintendo.. i have mounds of proof the account is mine (including tons of screenshots of interactions with my mom and cookie pulls, as well as physical handwritten crafting notes 😭) but is there any way i can do it without going through them??