Passkey logged me into another person’s account

I just recently made an account and was having a problem sending dms to friends.

I tried to deactivate and activate my account. When trying to log back in I used the passkey I made and instead of logging me in to my account, it logged me into a random person’s account. I can see literally everything on there. I immediately logged out and came here to post this. What exactly happened? Is this considered a breach of privacy?