@jespah,
Thanks so much for checking for me. It did say that Facebook for iPhone was the recognized device, but I read that the only way to have a device recognized is to use login notifications/approvals. When you do this, apparently you're asked to 'save your device', so that whenever you log in from that device it is trusted and you're not notified by email/text.
Under the recognized device it also showed a date, from back in September, so I'm thinking, did I do anything a few weeks back that would have set this up? And I just can't think..I didnt even know that this section of settings existed until i came across it by accident.
I'm just hoping there are others out there who have this in their settings and don't know how it got there - it would put my mind at ease.