In the early 1970s, as a teen, I hiked in Rocky Mountain National Park, going up the base of a mountain. The path went through a deciduous forest (there were brown leaves beneath the trees) and I saw oozing over some of these leaves an organism that looked like an amoeba. It was translucent blue, it had small particles contained in it, and it was about 1.5-2 inches wide (about the size of an oak leaf). It had what looked like pseudopods, and was moving forward by extending one over the leaf ahead of it. It was quite beautiful, as the blue was very clear. I thought it was a slime mold, as we had studied them that year in biology, but find out now that I was mistaken. I googled macroscopic single celled organism and found Gromia sphaerica in Wikipedia, but they seem to be aquatic, like the microscopic ones. Ditto Chaos carolinensis and Polychaos dubium, as far as I can make out.
Any light you can shed on this would be most welcome. I have never forgotten that little guy, and how beautiful it was.