My cousin was on this flight a few weeks ago:
flightaware.com/live/flight/AAL2 … N/tracklog
Just as they were about to land the plane went right back up. After a few min the pilot explained that there was something on the runway. They were 400ft off the ground when he pulled back up. Needless to say the pilot got a lot of congratulations when everyone deplaned.
It’s called a go-around, and it happens more often than most people think. In all probability, the passengers were in no danger, as it is a standard procedure for aborting a landing, and is in no way a “close call.” And 400 ft. is hardly low for a go-around, as the pilot can choose to go around all the way until touchdown.
Ditto that. At my old company we used to do balked landings also, where we would go around even if we had landed, so long as the TR’s and/or the speed brakes had yet been deployed. In fact during a CATII and lower approach it’s not uncommon for the mains to briefly touch even though the go-around was started at 100’agl, because of the sink rate and vertical momentum.
Even though it does happen now and then, you have to admit that it puts a scare into the passengers. You expect to land in a few moments and the next thing you know you headed back up. I know my pucker factor would be up. 
Of course people are going to be scared. Many people are scared of flying as it is, and when something unexpected happens, they will be even more scared. I’ve seen a passenger freak out over the flaps extending because they thought the wing was falling apart. People never cease to amaze me.
I just don’t want you to think your cousin was in any danger.
I remember being on a flight with a woman who was simply TERRIFIED! Every little bump and dip was cause for very audible moans and screams. Moments of light turbulence were very noisy times for the other passengers. The descent was like a descent into hell for everyone! 
LOL When the pilot idles the engines just before the flare, you could tell them the engines died. Just kidding.
Flew into STL many years ago (on TWA that dates it a bit) on the preverbial Dark and Stormy Night. An unexperienced flyer was upset during the flight and became increasingly agitated on very bumpy approach. Just before touchdown, engines when to idle and we glided a bit, smooth as ice. In the now hushed cabin, the entire plane heard her say “that wasn’t so bad”.
The PIC then flew the main gear into the ground. Reverse thrust up, spoilers out, rumble, bump, roar and a long terrified scream all the way until turn off.
ROFLMAO
Nice story jr 
A hard landing I encountered once - looong float, followed by KERTHUMP and oxygen masks clattering down 
- was followed by a very hushed taxi to the gate where the FA did the “Welcome to…” spiel and ended with “… and the last one off the plane has to go back for the hubcaps we left on the runway.” 