hmmm, I remember riding for far more years without a cell phone then I did with one, never had any problems. I once even got into an accident and had to go to the hospital to have my shoulder x-rayed so I called my wife using their in house phone. If your unable to use a phone due to condition the cops will figure out who you are if you put some sort of id information in your saddle bag.

Stop being so worried over forgetting the cell phone. For untold years that's what all cyclists did, and we did so without worry and fret, so stop worrying, you forget your phone just ride and think nothing of it. The more you worry about it the more likely you'll put yourself into a danger. There is such a thing as self fulfilling prophecy, what fears you dwell on can come to past.