Please first look at this - If your iPhone, iPad or iPod touch is lost or stolen – Apple Support
The insurance claim process will be determined by the insurance company.
The 'Find My' tracking is to help you discover if you left your phone in the office or the restaurant. Lost or Stolen phones are rarely ever seen again.
Are you saying you removed the device from Find My? If you just need a way yo het into Find My then in any browser sign into
cloud.com/find
typed in exactly like that
Risk mitigation
Get your provider to
Cancel your SIM.
Send you a replacement SIM on same number.
You can then put the SIM in another phone to get the codes you will need.
Phishing warning
Unless you had a PIN set on the SIM the thief or finder now know your number so don’t respond to texts to sign into your account!
Resign to the fact that if you had a passcode set then your data is safe but you will never see the phone again