They looked through the camera (SLR) and took the lens off. And yes they checked my keyring, and what they say is is that it was a purely random check, that every so many bags coming through get a thorough inspection.
Congratulations on your being able to get a knife on board a plane. You have been very lucky not to get caught. But terrorists cannot rely on luck, they have to plan, because if just one of them had gotten caught, it would increase the chances that more of them would get caught, not to mention that the US would know who to launch the nukes at.
And you are still evading the second point I raised, that somehow these four teams knew they would be on flights that did not have sky marshalls and that they could use their knives without fear of being shot.