Use 80lb dacron line instead of the sewing thread. You will get a lot more use out of it, and it won't take up any more space for about the same length.

Switch out to the fox micro whistle. Just as loud, but quite a bit smaller.

If I were sitting in camp with no food and nothing else to do and in a combat location, I would get busy making weapons/booby traps/alerting devices etc. You should give added credit to any student so inclined, allowing they are not giving away their location in so doing.