You seriously expect us to believe that some guy sitting in his car 20 feet away managed to spot you bumping into a bag and moving it two inches in pitch blackness?
(about 20 feet away from the bag)
20 feet away really isn't that far. It's probably about the length of 2 large trucks bumper to bumper.
The keyword here is 'about' so it could of been either 10-20 feet away. Rugged makes a good point on the distance, it's not that far.
As for "pitch blackness" I left out one detail that one specific angle was slightly lit by moon light, this guy was able to watch me walk past his bag while I couldn't see him well. I left this out because it's irrelevant, it's still loving dark regardless of the moon.