>>106199313
If you know someone's phone/email, you can literally just open a site/app and try to recover the password. If it says it sent an email/recovery SMS to them, you'll know that someone has an account on that site/app. Like fucking Grindr will tell you if a number exists in their database or not when you try to recover an account, lmao. Not all sites let you know if an account tied to the number/email exists in their database, but a fuckton of them do.