It seems to me that a similar post or two pop up roughly around this time during the last bit of summer. As always, it's the busiest stretch of travel. Couple that with the fact that the weather this summer has been abysmal, especially in the northeast corridor, and the fact that all airlines are posting record passenger numbers, can strain even the most gracious of agents.
As for your KTN disappearing, it's been a well known IT issue (surprise?), almost everyone I know has had their KTN disappear from their DL account. And it's an easy fix.
And agents aren't going to acknowledge a FAM, let alone tell joe traveler about one. So, it's a good possibility you were moved for one and that was what they told you (about the family of three).
My gut tells me that in the next couple of weeks, things will be back to normal and everyone will be much happier when the droves of once-a-year fliers stop traveling.