That's heartbreaking. Your only remedy is to claim on insurance, maybe your household insurance covers it?
Re what to do next please  look at this article and my advice after it.
 If your iPhone, iPad or iPod touch is lost or stolen – Apple Support
Tracking lost or stolen phones
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.
Risk mitigation
Get your provider toÂ
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
Its possible for a thief to obtain your phone number particularly if you did not have a PIN set on the SIM.  So do not respond to texts to sign into your account! They are NOT from Apple!
 Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support
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Resign to the fact that if you had a passcode set and you do not provide your Apple ID via phishing texts then your data is safe but you will never see the phone again.
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