Whoa... that's not good.
I concur. I was able to retrieve the soundcheck track from the "bad card" and my mac OS Disk Utility didn't detect a problem with the card itself.
I will note that the error occurred right as I pressed the REC button. I let my machine name the files with sequential numbers, and the soundcheck was MixPre-17, #18 does not exist, and then the Sandisk card contains files starting with #19.
No other issues with the deck all night. I will say it was in the hot sun, approx 100 degrees F.
Also, note that if you ever are patching out of a digital mixing console, do NOT leave a towel blocking the fan for the board. The computer in the board will shut down due to heat! (this happened between soundcheck and the set, right before I returned to the card issue)