I received a message from apple about my stolen iPhone but now I cannot open that message

Beware of a common phishing scam: You may get a text or email from “Apple” or “Apple Security” (or sometimes “Police”) saying your phone has been found and to click on a link to see its location. This is NEVER from Apple or from law enforcement; it is from the thief or fence to steal your Apple ID and identity. Delete any such message without responding to it.

If you clicked a link in that scam message and entered your Apple ID and password your phone and all of its data are now compromised, and and Activation Lock has been removed by the thief on your phone. Change your Apple ID password immediately (assuming the thief hasn’t changed it), and take whatever actions might be needed because all of your personal information stored on your phone is now in the hands of criminals. And see→If you think your Apple ID has been compromised - Apple Support

If you did not click on a link, or if you did you did not enter your Apple ID and password, you are safe. And if you go to https://icloud.com/find and still see your phone listed (even if you can’t track it) then you have avoided disaster.

No. You did not. You received a phishing message from the thief who has your phone.

If you used a link in that message to 'log in' to your account, you gave the thief your iCloud credentials, allowing them to remove the activation lock from the device.

Change your password. NOW.

You sure it was really from Apple?

Apple Support won’t know your phone’s location. It’s a scam to steal your account credentials.