This is why computers are NOT to be relied upon for capture. If you use the computer to capture, also record in the camera, be it tape or tapeless media. Because when Capture is aborted due to dropped frames in FCP, the temp capture file is discarded. Unless you have, in the USER PREFERENCES, ABORT CAPTURE ON DROPFRAMES unchecked.
Computers should never be used. Get reliable tapeless recording devices like the AJA KiPro or PiPro Mini...The Ninja or Samurai, Convergent Design Nano Flash.