(I'm posting this during the High Relentless race so it's possible this has happened, but just in case...)
Lap 15 is THE lap that players aim for in Heroic Races, trying to get that dragon... But at this point it's also the only lap that doesn't give you any kind of acknowledgement when you reach it. This always provokes a lot of posts to the forum (and probably contacts to SP support) wondering where their Heroic Dragon is or wanting reassurance that they'll receive it.
I suggest addressing this by inserting a title card at the beginning of lap 15 that says something like, "Congratulations! You've reached lap 15! You'll receive your new Heroic Dragon once the race is over."
It won't completely allay the confusion (since some people don't read), but I think it would help.