We’re sorry, but this is a serial number for a product that has been replaced. Please check your information and re-enter your serial number.

I lost my iPhone 12 Pro Max 3 days ago. The day I lost my phone I checked my apple care and imei code and everything. It showed everything was okay. But I checked my AppleCare to file theft and loss and suddenly there was no AppleCare and it said it has replaced this serial number. I do not get it. What should I do?