I had this as a kid and vaguely remember the plot: an English professor researching Bigfoot hires a camping guide to help track the elusive beast. They’re later joined by the professor’s plucky daughter. Strange happenings abound, but I believe there’s some sort of rational explanation for Bigfoot at the end of the novel. I can’t quite remember what it is.
Evarts, who died in 1989, is primarily remembered for his Westerns and mysteries, although Bigfoot was a popular entry in the children’s book phase of his career. The hardcover of the book featured a slight indentation of the footprint.