After 3 days fishing I finally got the lure, attached it, looked for the Aurelid pool but could not see it. Tried fishing all around the mob until the lure buff ran out. Nothing.
Some time later, I returned to the pool and Hirukon spawned as I stood there and I got the mount. I was dumbfounded.
Now my partner has gone through exactly the same scenario except Hurikon would not emerge from the pool, so I suspect the whole thing is bugged. So damn annoying.
Anyway, we will raise a ticket and I would suggest anyone else experiencing this issue should do the same.
Edit: my partner joined a Hurikon group and both they and the group leader, who had the lure, got the mount drop. There are obviously some issues with this quest.