Nope.

This is a lesson - just hope somebody returns it.

But with Find My iPhone turned off you've pretty-much given somebody an iPhone once they've factory reset it as it won't be locked.

Get the IMEI for the iPhone black listed 

John

Text it - depending on how notifications are set up, it may display the text message on the lock screen. If someone nice picks it up, they can read the text, and call you back. If it's someone not so nice, well, bye bye phone.

If the "Find Phone" feature has been enabled, then it is still possible. Is the phone locked with a fingerprint?

Joymarris:

 

If the "Find Phone" feature has been enabled, then it is still possible. Is the phone locked with a fingerprint?

 

op already said find my iphone is turned off.  It's literally in the first sentence.  

anyone know why a previously lost/locked iPhone, would suddenly become unlocked?

Someone restored it and knew the iCloud account?

gehenna:

 

Someone restored it and knew the iCloud account?

 

nope

is it only the original owner that can unlock with their iCloud account?  The lock doesn't time out after a number of years or something?

It's indefinite. I think the device can be removed from an iCloud account in the web portal of the owner, so maybe that happened and when the iphone was restored and did an activation check it found it was no longer associated with an icloud account.