It would take a bit of time to write out all of the code, but here is the approach I would take:
Instead of placing the objects somewhere and then using some technique to know when they are in the right place, put them in their right place.
When you enter that screen, have each object store its own location, and programmatically move it to the start point. That might be a random location, or some other rule that lays them out neatly. Store that position too.
As the user drags the object, use Pythagoras to calculate the distance from the stored right place location.
If the distance is less than a certain tolerance, use a tween to move the object to the right place location, in a short amount of time.
If the distance is more than a certain tolerance, use a tween to move the object back to its stored start location, taking more time.
Both ActionScript and CreateJS have tween libraries built into them.