Unlocking 'Lost' iPhone

Thank you Roger but it was not as it seemingly should have been.

I recovered the phone, presumably unlocked it, since I then sent a message to my partner to say I'd recovered it. I drove home, took the phone out of the car cradle, and the screen then read the 'Lost Phone' message which gave me just 2 options. Call the number I'd attached to the Lost Phone message or use it in emergency mode. There was no way I could see to get to the screen that would present the login/passcode option. I then contacted Apple Support who asked me to find another iPhone through which I logged onto my icloud account and re-activated the phone. In the meantime I had logged onto the Apple Support site and read through all the 'Find My Phone' info and could find nothing about how to unlock it in my situation. Seems bizarre I was able to send that initial text some 30 minutes before the 'locked screen' presented itself.