Actually had something similar happen and you have look at the obvious here, to which they or anyone else cannot deny.
You lost the card. Get a new card. Send everything you would normally send and the photo of the new card. It is feasible to lose a card after using it, it happens at some point right ? They cannot expect magic and cannot deny payment. That would be illegal.
They can even send and will send the payment to the same source, the same card. The bank will say “yea that’s cool.”
Don’t lie. They can assume you made a fraudulent payment and use due diligence to make checks, to find you didn’t. They have zero reason to withhold your money.
Also, make a token deposit with the new card and then withdraw that too. Everything will check out because there is no reason it can’t. Losing a card between buying and refunding (depositing and withdrawing is the same thing really, using the same process) is totally normal and happens all the time.