My account has vanished here, but after re-creating it, my old posts are still available. What is this?

I remember I had registered an user here, in order to ask questions. Today, when I tried to log in, I couldn’t. Then I clicked on reset password, but surprisingly it told me there was no username associated with my email. Basically, my account has vanished into thin air. However, when I created a new account with the same email that I tried for the previous log-in, my old posts and activities are here.

What is this?..