Aha......I had used waitusb=5 when I was running the other boot codes using UUIDs.
I could have sworn I must have tried using waitusb=5 on reboot when at least one time when I was trying to figure out what was going on. But maybe I didn't. Because.....lo and behold...when I put my usbkey in now, downloaded Firefox and then rebooted using the waitusb=5 command. It worked.
And I don't seem to be getting the error that I got on at least one attempt. But I guess somewhere along in the process I must have resolved that issue. Perhaps I used the waitusb=5 when I was getting that error and when that didn't work, forgot to try using it again when I tried remaking my key again.
Oh well... But now I get to start the New Year doing a little bit more exploring of Tiny Core.
I think you guys might actually have quite the little gem here just from very first impressions.
Happy New Year Everyone. And thanks Gerald for your comment. I thought I had already done that but it made me go back and try it again. And this time success.