My iPad keeps asking for my friend's iPhone passcode

Recently I lost my iPad and tried finding it through Find Device on my friend's iPhone browser. I did got the iPad back but, now when i login it keeps asking for my friend's iPhone pass code as an additional protection. I checked my account settings too but there wasn't any other device listed or additional protection. Now i can't ask him for his pass code, just seems too much to me.

Please help me in this as I'm unable to login into MY OWN DEVICE.

[Re-Titled by Moderator]