Little Grass Frog

I think you are probably correct, based on the habitat and size especially. I looked at my other pictures to see if the spot was on both sides and it was not. The little thing caught my eye during a phone call and I had to follow it until I hung up!

Based on the tiny size of the frog, the location you spotted it, the apparent whitish belly and the dark stripe that runs through the eye I think it is a Little Grass Frog (Pseudacris ocularis). The spot on the side looks to be a small piece of the black dirt that it is sitting on. Congrats on spotting one of these, they are quite hard to find due to their tiny size.