Its a bug, for some reason it doesnt always generate the correct crash site.
if you dont find what youre supposed to, reboard your ship and look at the left navigation panel again. You should now see two crash sites at the same location. (The second crash site doesnt appear until you reboard)
select the bottom one, take off and jump into supercruise, immediately spin round and drop back in, you should now be about 20km away, but you will be at the right site.
ive tried relogging, doesnt always work for me, but i guess others are lucky
ive found crash sites when scavengers spawn are usually the right ones..