I need to disable auto-unlock

The Chevy Volt 2013 key fob is not waterproof so I can't take it with me when I surf. The other options are to hide it on the car (dumb i know, but we surfers do that all the time) or put it in a lockbox attached to the door handle. But this auto-unlock feature - where the car can be opened if the Fob is anywhere nearby - makes it all impossible (it even activates through the metal and plastic of the lockbox.) I looked in the manual and there were vague allusions to disabling some parts of the fob but i followed the instructions and absolutely nothing changed. I admit this could be pilot error. I think there must be a way to disable it, but it sure is complicated.

I looked at the fob so I could pull out the battery. Couldn't find a hammer-less way to do this. Also I fear this will stop the car from starting.

I went to a locksmith. They can make a key for the door but the Chevy wouldn't start with it. They tried to program their microchip to no avail.

Chevrolet says "We've never had this issue before." They had no advice on how to disable the entry, and insisted that they don't make keys without the fob. This is dismaying to me. The very technology that is supposed to make life easier is making my life very very hard. It's pretty absurd. I just want a KEY. That's it, for goodness sake. Does anyone have a solution to this?