Scary Worm Snake Thing

OK scared myself on a nighttime walk with Penny again but this was for a good reason. Right there on the sidewalk was what looked like a worm or a snake or something. It was thin and tapered on the ends, it didn't appear to have a head, it was dark brown or black, it appeared to be smooth maybe even wet, and it moved in waves sideways. I ran away from it, the dog went to the bathroom and by the time I came back it was gone...Probably slithered into a bush or the grass. I searched the internet to find out what it could be but I couldn't find anything that matched it. It might be an earthworm but I didn't think they moved in waves like that. I thought they inched along. The best way to describe this would be a very small eel. It was dark so I may not be describing it exactly how it would look in the light but I thought this was very freaky. Fifty points to whoever finds out what this might be so I can walk in the grass without fear.