Wildlife photos developed with only a ufo in pic

While on a camera trip to local lake I took a 35 mm photo of some ducks flying overhead.  I had taken photos of oddity things around lake before and after pics of ducks.  When the film returned, no ducks, but a tiny blue and red winged object that appears to be banking in the photo that I still have.
Altitude of object was probably 2000 feet and sky was sunny and clear.  I was a cross country surveyor for twelve years during that time.
Witness indicates that the date of the sighting is approximate.  PD