Sounds like you have two factor authentication turned on and it asked for your approval.
First of all, having this on potentially saved you a lot of hassle so good job there!
Secondly, you can't view the notification again as far as I know!
Thirdly, if you've not changed your Apple password for a while now would be a good time.
Finally, this happened to a family after they entered their email address on a site that wasn't exactly so be careful what you sign up to!