At the same time I've never had a flashdrive fail due to temperature or water. I used to do printer repair for a fairly large company and on the printers I worked on firmware was loaded just by plugging a flashdrive into the usb port on the printer. I always had a pocket full of flashdrives because of that. Over the years I've probably forgotten at least a dozen flashdrives in my pocket when I washed my pants and at least half of those wound up going through the dryer too. They were all still completely functional afterwords. I also live in MN so I've left them in my vehicle when it's -17F outside and had no issues.
The only things I've ever actually seen kill a flashdrive are major physical damage like you said, or just general wear from plugging them in and unplugging them too much. Technically I guess I also killed one by messing up a format badly enough but that's a whole other issue. As far as physical durability goes the full metal body Kingston Data Traveler drives have always been durable enough that I could just shove them in my pocket and not worry about them. I'm sure there are others like those but those are just what my workplace bought in bulk so they are what I typically used.
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