It is hard to tell from this one track. The lighting makes it difficult to see a good outline of the track. The track is in poor condition and it is obvious that the track is several days old because it is full of debris.
I am not convinced that it is a mountain lion track.
I just measured the front paw of our Lab-Rottweiler mix with and without pressure on it and it measures 2.75” long x 2.5” wide. This was done on a hard surface.
The measurement of my thumb from the base to the tip is 2.75” long. Using this picture it would appear that the track is not as wide as your friends thumb is long but it does appear to be the same length.
According to the site given below the average dimension of a mountain lion track is 4” long x 3.75” wide. This is the size of my palm. A bobcat’s track is approximately 1.75” long x 1.875 wide and a coyote 2.5” long x 2” wide.
My guess is that this is an old coyote track.
Thanks for sharing, this made me investigate a few things and I found it entertaining and educational.
http://www.cougarsanctuary.org/tracks.html http://cahe.nmsu.edu/pubs/_circulars/circ561.html