So, I emailed Rick to find out what the story is behind "Rock" and here is the answer in his own words:
Q. Who is rock?
A. Well many of you have had the privlage of meeting rock in the past. He is often with me even though you don't often see him. Rock became a travaling companion of mine in the Spring of 2001 when I was living in Hermiston, OR. He found me when I was walking Kimsey and Bromus along the Columbia river. He is a glacier eratic rock that was washed down out of Montana during the end of the last ice age. Since he joined me in 2001, we have traveled to Latvia, Luthiania, Kuwait, Iraq, Germany, Denmark, Eygpt, Isreal, Ireland, and Japan. We have also traveled in so many US states that it is hard to keep track of them all. But the list includes Alaska, Maine, Georgia, and Oklahoma. We have gone swimming in the Mediterainian, Red Sea, Pacific, and deep sea fishing in the Atlantic. Needless to say Rock has no moss growing on him. So thats rocks story.