So, imagine you are a used airplane salesman. You are taking a prospective buyer on a test flight when out of the blue (literally) a wheel/tire smacks into the plane and takes out a chunk of fuselage and the windshield!! Now imagine that you are the pilot of a Cessna going for a flight when you hear a clunk and in talking to the tower realize you have lost a wheel/tire off of your aircraft. Now you have to land the beast without a wheel on one of the landing gear.
Fortunately both aircraft made it to the ground safely with no injuries. What are the chances that a part falling off of one aircraft will just happen to impact another aircraft flying a few thousand feet below it?
Bad day indead but could have been worse.
16 minutes ago