I could send her the claim form, but U-Pic will most probably deny it because it shows a signature.
Don't assume things before you did not check. This is not an uncommon situation. We ship with DHL and our parcels are insured. In cases like this, DHL only requires a signed confirmation of the customer that he did not receive the parcel and then we receive the insurance money.
So check with the insurer and your parcel service what they require in cases like this - a written confirmation or a statuatory declaration by the customer. Then send him the form. If he did receive the parcel he most likely will back of, he will write you an email that his son received the order and did not tell him or such nonsense.
If he sends you the form, claim the insurance money.
If the insurer or the parcel service tell you they do not want to have anything to do with the matter, they have a signature and that's enough for them, send the customer a form like this we use:
Written Statement Under Penalty of Perjury
I certify under penalty of perjury that the following statement is true and correct:
Personal Information
Family Name: _________________________
First Name: _________________________
Address: _________________________
_________________________
_________________________
_________________________
2. Declaration
I hereby declare under penalty of perjury that until today I did not receive the DHL Parcel No.
11111, with my order from [date] from John Doe Enterprises.
Date, Signature
...
If they sign this you can then compare the signature. If it does not match, then assume they are telling the truth, send a replacement or return the money. Then go to the police and file an investigation enquiry. Because then someone must have forged the signature and stolen the parcel - most likely the driver from the parcel service. The police will then investigate.
That's at least how we do it and did in the past.