MOV file only playing half of the recorded footage

Hi, I've recorded some footage using a Camsports HD-S 720p HatCam which has 4Gb of internal memory - this is enough for approx 1 hour 30 minutes of footage. The file I've got is 3.7Gb but when I play the file, it says there is only 34 minutes of footage. Normally 30 minutes would take up just 1.3Gb. I've tried various recovery tools but they all say that the file is just 34 minutes long. Anyone come across anything similar or know if I can recover the missing hour ?

Thanks in advance
RB