In reply to G1ZJQ:
I did this once on Worcester Beacon WB-009 - I left the RG213 in the car. Strange, because I used to carry it by wearing it like a sash and how I missed carrying it I don’t know. Fortunately I had a couple of patch leads which let me get the antenna to all of 3 feet off the ground. I now use 5D-FB 9mm semi-rigid which fits inside the backpack.
I was going to suggest the obvious - make a checklist covering the kit, clothing, food, etc and print a copy off before each activation, then tick off the items - but of course that doesn’t prevent brain fade on arrival at the parking spot!