With due apologies to GoPros...................................have recovered all recocordings. It seems that the recording for one hour and 4 and a half minute was saved and then further recording was made in a second file and continued till the end. Have seen all four now, i.e two runs with two camera. The confusion was that the original recording starts in say file GoPro0275.mp4, when it stops in this file and saves, it records the remaining vdo in file by name of Go0010275.mp4! Now because I had set the file view to view by name, this second file is shown not next to the GoPro0275 file but well before all GoPro***** files. When i was rechecking, I thought that these were earlier recordings and hence stacked up before, and initially I thought they were portions of recce run, but than it all cleared up. So essentially the last 4 numbers i.e 0275 remains same, but the first bit changes.
So we are all good!