Black streak in sky above Maroon Bells

I took a picture of The Bells in front of crater lake. I then moved my camera slightly to the left and snapped another shot seconds after. I didn't see anything in the sky; however, upon reviewing my pictures a few days later I noticed that there was a black streak in the upper corner of the second picture. At first I thought something was on my lens but my hypothesis was quickly overturned when I could not find a similar smudge (or any debris for that matter) in any of the other photos I had taken during the four day trip. I don't know what the black streak is but I think whatever it is happens to be moving so fast that my camera could not capture its image appropriately.