I cannot see ankle, personally. Have you ever carried a kbar at the ankle? They are heavy and misbalanced unless he was wearing mid high to knee high boots, but not with tennis shoes and socks unless he maybe had a special pocket in the lower part of the pants and nope, I just cannot make that work. Not at all without heavy boots, compression socks or an ankle sheath, which he apparently did not have. Tucked into the back of a waistline, yeah a lot of posers do that so possible but totally stupid. People who know how to handle knives don't want to be juggling a sheath on the move, but then here we are.
My favorite is a horizontal back of belt sheath or thigh holster sheath, easy access, no flopping, stays with you, slide it out, cut your rope for camp, slide it back, foldover snap, not one of those around the top of the grip things. ( see how I slide in a non murderous use for a knife

)