Mystery solved it is a dime that was on a railroad track at one time and there happens to be a railroad track on the next block where I found it. Both weighted 2.2 grams.
Just yesterday I happened to be working at a spot next to some heavily traveled train tracks where the trains were coming by every 15 minutes or so. I actually thought about this thread and decided to reminisce about my childhood by putting a few pennies, dime and nickle on the tracks. After the train went by I was only able to find two of the three pennies and the nickle was gone as well. One of the flattened pennies was very oblong in shape, but the other was quite round. The dime also came out fairly round. I ended up giving them to a couple of kids who were watching me (I was probably a bad influence on them). Point being, the coins can come out round, but there are probably a lot of variables to it.