Some MPEGS strop working after watching

I took some footage with my drone yesterday for a client. Just to check things before I got a chance to edit, I checked the raw footage was there and in good order. I watched both the files of footage I took, both worked and looked as required. However, this morning when I went to edit them, one of the files has reduced in size and I get the message "The document "DJI_0260.MP4 could not be opened" "This file isnt compatible with QuickTime Player". The footage was there and perfect yesterday, I did nothing at all to the footage or the scan disk it is currently stored on. I am hoping someone can help me here as tyhis footage is pretty important to my client.