Did you sell it through this account?
If you have refunded the buyer, you will have to try and make a claim against the carrier.
How successful you are will depend on who the carrier was, the service you used and the level of insurance.
You will also have to have evidence that the parcel was interfered with and items stolen.
If Royal Mail deliver opened items, they put the parcel in a plastic bag - something like that would be evidence for a carrier.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)