OMG; United!
Firing someone who thinks it's suspicious to have someone scribbling ambiguous messages at that particular place high up in the air... come ON!
If you can scribble this, you certainly can fasten a little remote controlled irritant wherever you wish on the plane.
These anomalies is what makes Mossad so good at what they do. They follow up on them. In High Security Amurca; unless it's in a plastic container bigger than 100ml it is not dangerous. Do you sense the irony?
What I'm trying to say is that if you need or want to be paranoid you must be paranoid of the unusual, not the usual. Terrorists always finds way to pass the usual, the standard airport security. THIS is unusual. THIS should concern parties involved.
Sadly those concerned got fired because the threat/whatever was unusual. Ridiculous.