I'm back in Revelstoke after ten days at a hiking lodge near Golden, BC. Since there's a supercharger in Golden, I parked the car with a nearly full battery. Of the ten days I was gone, the first week was extremely hot in town (typically over 30 C) and the next three were cooler. I have version 2018.24.8, which Tesla pushed to the car when I phoned them about the issue. I was very careful to turn everything off, and I shut down the car from the screen. Walk-away-lock didn't seem to function, so I locked the car with the key card. As several people have noted above, the Model 3 does not have an energy-saver mode.
The car lost just over 100 km of range in the ten days, which left me with plenty of range to get back to Revelstoke, where I am now. This is half as much as it lost while I was at the lodge near Burton, BC, but twice as much as the 4 miles per day it lost when parked at the airport a few months age.
To answer some of the questions raised above:
I have no third-party apps.
I have not noticed any issues with the charge-port door or the brakes.
The car was definitely outside of cell phone range. (My phone, which is on Verizon in the US and Telus in Canada had service, but the car, which I think is on AT&T in the US and maybe Rodgers in Canada, did not have service.)
The J1772 charger in Nakusp is by a company called Flow. As noted in my OP, they didn't answer their phone.
This is all a big disappointment, as it means I may have to cancel my last week of hiking, which will again be the the lodge near Burton. If I lost only 100 km of range that week, I'd be fine. But if I lost 150 km I'd be unable to make it to the nearest charger. In a few days I'll be going up to another hiking lodge here, where I'll only be 5 or 10 km from the supercharger, so I'm not concerned. But that last week looks like it's shot. I'd have to find an indoor parking spot, and that seems unlikely. And the report above of the car parked in a hanger and still loosing a lot of range, makes me even more wary.
The Model 3 with EAP is marvelous to drive. I'd say that over 95% of my highway driving is on AP and the car is driving itself. But unless there's actually some defect in my car, which I doubt, as I know the car has to cool its batteries to preserve their lifespan, it looks as though, at least for the time being, the Model 3 really has to be plugged in if the weather is hot. This means that for back-country trips, the car is not yet practical. I wish there was an option to truly shut off everything but the Bluetooth and RFID card reader, for this kind of use. If I had known then what I know now, I'd have driven the Prius up here. The lesson I've learned will cost me a week of hiking, and there's no refund. It's an expensive lesson. Until chargers are as common as gas stations, there are places it will be risky to take an EV.
Well, the week of hiking I lose will give me an extra week to do my breath-hold exercises for my upcoming freediving trip.
I still love the car. I'm just learning its limits.