Sometimes I don't get coins from doing a hauntlet run - I understand that you need to finish in 3:30 and your character has to actually cross the line to get the coin.
Sometimes after someone crosses the line ahead of you and the pop up saying your time is displayed, even if you cross before 3:30 is up the coin is not given to you.

Example: in my run just then, someone cross the line at 3:01 or similar and I crossed about 10 seconds after that - no coin.