idk what i saw

i dont know what i saw.so we were driving on the highway and i was loooking at this hill.then outta no where i c this like medium shaped oval shadow go acrosss the hill.then it just go overs and its gone.it kinda moved the way the hill was shaped.it wasnt very faced paced but it wasnt slow either.but i lookd at the sky and nothing was there.it coulda been someone on the ground doing sumting but still...doesnt make sense so thats wats puzzling me