Sure, go to
http://appleid.apple.com
log in using your iCloud credentials.
Then go to Password and security, and next click on "Trusted devices"
Chances are, your old phone is still there
🙂
However, for future reference, please note that if you sell the phone and the new owner sets it up with their own apple id, the device will disappear from your apple ID account. In your case, the phone is still there because you haven't restored it or no one else has activated it.