Hello, the script call to check if an event was thrown at a specific spot is:
$gamePlayer.hasThrownEvent(eventId, x, y)
But if you want to 'play' the event when it reach the ground (anywhere), use the notetag: <pickup event: A> where A is the id of the self switch of that event. So when that event reach the ground after being thrown, it turn it self switch A ON, and whatever happen on the new event page is up to you.
Hope that help.