Same shit happened to me a couple of months back. Seven from the Black Bachelor. My girl did a gagging scene and he was "sick" and couldn't cum so I came in half way through and provided the nessecary pop.
Apparently he didn't have enough cash on hand to pay her so she got shorted. When we called later to ask about it he said he shorted her because "she didn't make him cum" and as for me he doesn't pay for male talent. Last time I checked it's your dick is your responsibility. And not even a thank you for salvaging his shoot.

Oh well lesson learned, My advice is no release form gets signed before the cash is in hand.