...So the proper answer to your question is : don't allow yourself to be in a situation where the horse can take off, stretch its neck and snatch the reins from your hands. By all means talk to your companions but don't relax your concentration of steering and controlling the horse. And as for riding on a long loose rein rather than collected with a light contact with the horse's mouth - well you are asking for trouble - going out or coming home...
I'll have to disagree with you here. I have a hard time imagining a cowboy riding "collected with a light contact with the horse's mouth" for a 10 hour day, working cattle while maintaining his "concentration of steering and controlling the horse".
I don't think I've ever seen anyone trail ride in southern Arizona with constant contact.
I did have one experienced rider tell me that was how I need to ride Mia - to never let her go more than a half dozen steps without giving her some direction. If that is the only way to control her, I'll sell her to someone who wants to ride that way. I've had her for 4 years, and she is the horse that made me interested in riding, but if that proves to be the only way to control her, she's gone.
I'm more likely to try this:
Any horse I ride that tries to bolt had better stop in about 2 strides because if it takes longer than that I'm going to stop trying to stop the horse and go to spurring. The runaway doesn't last long after that and rarely happens again...
That may explain why, when my former ranch horse gelding gets really scared, he locks up. Feet apart, head up, nostrils flared...and not moving a muscle. He's only been that scared a couple of times, but I find that highly preferable to running away. He may have been taught that bolting means you immediately enter hell itself. I don't mind the idea of once a year or so encountering something that requires me to get off the horse and take a couple of minutes rubbing his neck, and then mounting and going on.
I also don't have the option of desensitizing her to everything. I cannot desensitize her to a partially buried thorn on the trail, or a rattlesnake coiling up next to her. And in a land of rock and cholla, I cannot afford to have her running mindlessly (Internet image, but looks like the area around me):