As Mamabear has indicated, we do not have enough details to assess his individual decision, so I will not comment on his particular case.

[Rant on]

What does scare me is the paternalism running rampant in society today. No one is responsible for the consequences of his own decisions and actions or omissions. It is always the fault of someone else. Thus we conclude the rental car company might be at fault in failing to warn.
Should it have given him a printed list of warnings and recommendations? Then should it have further concluded that anyone actually needing such information would also be so stupid, careless, or incapable of reading and comprehending that it need to emphatically summarize them for him orally (assuming such a person would also listen)? We assume that the vehicle was inextricably stuck in an area where it might reasonably be found or noticed.

I have no doubt that travelers could overlook a 1.3 cubic feet water container, one weeks supply of food, a tent, and possibly other tools and supplies. Furthermore it is also possible one might not look at a map before leaving his well-provisioned vehicle, or even conclude that he could walk several hundred kilometers through a wild/desert region in 100 degree Fahrenheit temperature. But somehow such behavior does not seem very foreseeable or reasonable.

It is the paternalist regulation of business and life that has given us unnecessary and ridiculous warnings. Thus we have owners manuals for cars that are hundreds of pages long inflated with safety recommendations, pictures, and diagrams of every potential hazard. Match boxes are emblazoned "KEEP AWAY FROM CHILDREN," and "CAUTION: CLOSE BOX BEFORE STRIKING." If you buy a Ruger firearm, it comes with a warning engraved on the barrel to read the owners manual before use.

ENOUGH ALREADY. Does anybody really believe that these warnings do any good?

Justice Hand said it best nearly a century ago: The business of life is better carried on through the use of dangerous machinery than not. We cannot make life foolproof. Somebody will always find a way to hurt or kill himself. We need to demand that people behave reasonably or else suffer the consequences. We cannot so dumb-down and restrict life to fit the lowest common denominator without sacrificing many of the things that make life fun and productive.

[Rant off}

John