If the passenger hadn't gone to the media, would it have become a story ????
Perhaps not, but we don't know the exact circumstances on board. We don't know if there was panic among passengers. We don't know if an inexperienced stewardess freaked out, leading to panic amongst passengers. If any of this took place, that's would be a story in itself, even if the underlying cause (a leaky seal) was a non-event in safety terms.
As to how the story got to the press: most likely a passenger was either a journalist himself or knew someone who was, and decided to sell the story and picture for a few quid.
The story would have been through in-house lawyers at the Mail prior to publication. The Mail would appreciate that Emirates is a big newspaper advertiser and has deep pockets to defend itself against libellous damage to its reputation. So for that matter does does Airbus. For both these reasons, while the tone of the story may be complete
, the story itself probably has enough truth to it that the Mail cannot be attacked for publishing it.