Depending upon what data that a data recovery professional finds on the card you might have to follow a different line of investigation: and in any case the answer to the question below will likely assist the data recovery exercise.
Can you confirm that YOU saw an image review from the card, in situ? (when at the shoot)
This is a very specific question. I am asking if you at any time on the shoot saw an image review that was FROM THAT CARD (not camera memory).
The questions is predicated by your statement that when the card was REPLACED in the Second’s Camera it read “Card Error”.
That statement allows for several possibilities, including that the card was always faulty and no images were ever recorded.
WW