Yes, this is a vestige of 9/11.
The bag contains 3-5 day supplies of Robert's various medications, of which there are now fewer, extra extension tubing, syringes, dish soap, formula, diapers, measuring spoons and cups, usually some bottled water, and other things I can't think of now. Oh, yes, his back-up enteral feeding button. Everything I'd need to take care of him while on the run from disaster.
It occurred to me this might be a good idea on 9/13 when I called the research scientist with whom we were working, in a panic, because I realized that we had placed an order a few days earlier, probably the 7th, which had been a Friday, for the special solution that would dissolve Robert's Prilosec (his anti-reflux drug at the time) so that it could go through his g-tube. Without the solution, Robert would have been hospitalized within 48 hours. The research scientist was in Missouri. We were in the DC area. All flights in and out of WDC airports had been grounded as of about 10 am on Tuesday morning.
We were lucky that time: the FedEx plane with our medication on it had landed in the early morning hours of 9/11. The shipment had been delayed leaving the airport for security reasons, but was on its way to us.
This was my Scarlett O'Hara moment (minus the racism): as god was my witness, we would never be without medical supplies or prescription medications again. I am still unable to prevent myself from hoarding medical supplies. I use each and every tube and syringe until it can be used no more. I order my medical supplies the day the insurance allows another order to go through.
Ah--the green backpack--the symbol of the god of chaos and circumstances that roil beneath the thin, tensed surface that pretends to stability.