Q: Video Disappearing from IPHOTO

I am using a Macbook Pro and IPhoto version 9.5.1

On a very regular basis I upload video and then view it on IPHOTO, it is there. Then I look for it again days, weeks later and instead of the video being there, the date still exists and a Gray Palm Tree picture is there as a placeholder and when I scroll across it says there are no files there ("0"). Is there some other place to find the video? Why does this keep happening? Why does it leave the placeholder if it doesnt recognize the video?

Thank you