Did you have Find My activated on your iPhone before it was lost? If not, then you are not going to be able to locate it. You have mentioned that you are not able to see the lost device under your Apple ID. If that is the case, then you are definitely not going to be able to locate it.
Questions for you: Did you get an email or a text from anyone that stated that your iPhone has been found and that you have to go to a website and enter your Apple ID and Password? The reason I ask is because if this happened and you entered your Apple ID and Passcode on a fake website, then the thieves captured the information and removed your device from your Apple ID.
Axel F.