I'm not a naysayer on the bandana. I understand its importance. However, I feel like a bandana is not that difficult to replicate by using my knife and the clothing on me. Of the 4 things mentioned here, the bandana is priority #4 for me.

For those who could not replicate a bandana from a knife and their clothing (or somebody's clothing, a drape, or anything similar), then carrying a bandana would be useless for survival anyway. They would forget why their significant other packed it in their bag. A minimal level of creativity and skill is required in an extremely unusual disaster like 911.

I wonder how many people died in 911 because they were stuck below rubble without a whistle while nobody could hear their voice, or without a flashlight to see a passageway out. I guess we'll never know, but the number of people who died this way has got to be more than zero.