The thing with people grabbing their bags during evac has been in the news after the last couple of incidents.
Last night I read an account of a woman with newborn on the Frontier flight in Denver. She didn't get any of her bags as she was carrying her child. The passengers were kept in the terminal building in an isolated area while they were accounted for. Then they had to make arrangements for overnight stays, alternate flights, etc. Apparently, getting peoples carry on bags off the plane is a low priority when this happens. This woman had none of the supplies which are normally carried by new parents carrying infants. She claims at one point she asked a Frontier rep about where she could obtain diapers, and the other things she needed and was told by the rep that she "should have brought that with her when she left the plane". If this were true and happened to me, there would most likely be an assault charge pending.
But this begs the question; What if you have meds or some equipment or item that you must have to survive? I have some meds that if I go a couple days without, it's going to be bad. When I travel, I always carry 7 days extra beyond what I need for the trip and they always are in my small backpack that goes under the seat. So if I have to evac an aircraft in a situation like this, is it okay to be "that guy" and grab my small day pack? Or open up the pack and get out the meds before deplaneing? Or plan on a hospital visit to try and get restocked until I either get home or have someone mail me the meds from home?