One idea in that situation, if you were the person talking to the one who dropped the phone would be to quickly conference 911 and the friend. The phone companies will do it for a small fee now so you don't need to have that service on your plan.
Also make sure your cell phone in always on you. Women are bad about putting cell phones in their purses and besides being annoying when there is a ringing purse sitting on someones desk if someone grabs your purse and runs or you fall and can't reach it then you can't reach your phone. Alway keep it on a belt, in a pocket, etc.