Last known location is only available for 24 hours. So if a thief erased a device more than 24 hours ago, there will be no way to know if find my was enabled at the time of theft or not.
For AIG or any other insurance to claim that they can no longer ping or see a last location shown is not evidence Find My was not enabled when the device was stolen. That’s the very issue. If someone did indeed enable find my on their device before it was lost or stolen, and it has been more than 24 hours, the insurance company, nor anyone, has any means of knowing whether it was, or was not enabled prior to the device disappearing.
We’ve seen posts like this many times since AppleCare+ with loss and theft was first offered. I am not at all convinced that the insurance claims agents have any clue how Find My works. They have no means of independently verifying it was or was not enabled before lost or theft of the device has been erased a day or more ago.
Showing a screen shot or something that the device is still activation locked - I.e. tied to and listed under the owners AppleID as a trusted device is the best evidence they did indeed secure their device prior to loss. Simply not being found in Find My, or no last location found, is not evidence they did not enable that feature prior to loss.
That is the issue with these insurers who insure any and all smart phones, but whose adjusters and online support people seem to not understand the specifics of the remote tracking versus anti theft tech different smart phone manufacturers provide.