I can't see it being a real issue in normal life.
You are absolutely right Luci as you draw the bow it is pulled snuggly back into the palm between the thumb and forefinger. However once you loose, the bow jumps forward both from the momentum of the string and the extension of your compressed bow arm. If you do not have at least a loose grip on the bow you will lose it. I have done this once when shooting without my sling and forgetting I didn't have it. Very embarrassing!
Here's a link to a page where you can see some bow slings. http://www.quicksarchery.co.uk/super...1090/Bowslings
My choice is the simplest one down the bottom left (not the most popular choice by the way). Essentially thumb and forefinger go in the two rings making a continuous loop from thumb, forefinger and sling with the bow inside it.
And here's the best picture that I could find showing how the bow is not really held at all. Note styles vary enormously, for example I don't curl my fingers up like this archer I just let them hang loose. http://www.london2012.com/photos/201...2008-60743.php
Of course for a fantasy story you wouldn't be using such devices but I believe you would still try to have a loose grip on the bow whilst shooting.
Bottom line, when shooting, your bow arm wants to be an inert rod whose only job is to keep the bow away from your body! You want as little muscle usage in that arm as possible as that will tend to spoil your aim. It seems a bit counter-intuitive at first but actually the same is true in the drawing arm once at full draw. As much as possible of the work is done by your back muscles.