Earlier quoted context omitted.
Did you ever set up SMS 2fa? Did any of your contacts use the Facebook app to sync their contacts (at least at one point a default behaviour)? Then Facebook has your number. I remember when I still used it being promoted by a bar at the top of the web UI "Is this your number?" With my actual number suggesting I add it to my profile, so I know they have mine.
Despite using 2FA and listing my number on my profile - albeit restricted to "just me", I don't appear in the data. It's not as simple as they just having a record of it somewhere.
My wife's number isn't in there, either. I'm just really surprised, because I checked facebook the other day and it said I was searchable by email and phone number.
I even searched my email address, and a lot of other breaches show, but not Facebook.
I guess I got lucky?