I've never been in the military, but I would think that some form of communication with your rescue team would be paramount while you're in hostile territory. Since you said you normally keep your signal mirror in your TAC vest and that gets left behind in the burning chopper in this exercise (I assume all your other communications gear as well), I'd want a second mirror in my soap dish! I'm not sure a whistle would do much to attract your mates in a rescue chopper, it would just alert the enemy wouldn't it?