Thanks now lets focus in the puzzle, 0.024btc are good motivation to find that privatekey, as hint we know the key start with 5,
hold on a minute, the dude in the video explicitly says he is using compressed key for this one so it starts with K or L, since the scrammed thing doesn't have any L so it must start with a K. additionally the char count of it is 52 which is another indication of it being a compressed key
by the way where are you guys getting the "scrambled" key from? i couldn't find it anywhere in the video.
How do we validate that the winner is not a friend or family member? Well, it's basically impossible and that is the main problem I have with these puzzles. 
if the thing to solve is real then there is still a chance for others to solve and claim it faster even if the creator has the key! you can't verify its solve-ability unless the prize is claimed and OP explains how the puzzle should have been solved.