Correct, Pete is a well known artist and has done artwork for the BFF. The Painted Cave website has been up for years but does not appear to be active in the 'store' category.
Pete Travers has been associated with many movies that are listed on his resume. Pete Travers is in the entertainment industry and the sketch project is small potatoes.
There is an interesting section on the Painted Cave site labeled "Patterson/Gimlin Film Frame Sketch". The sketch is an overlay to the original but I am not sure what 'original' was used.
He added a statement that 'the sketch has no real scientific value'.
Recently, there have been digital clown shows modifying the look back image and they have been very bad. Since very few people have had access to the original PGF, I wondered where they found an image to modify. Book cover? Perhaps. Internet with low resolution? Maybe. Without overlaying the overlaid image(s), I guess that Pete's image was pirated and used as the image to trash.