Yes, I tried that. Didn't work. I eventually gave up all reasonable fixes, and decided to try some weird ones. i logged off my account without rebooting, and logged on to my guest account. Lo and behold, the battery icon was on the taskbar. I logged back on to my account and the icon was back there too. I have no idea why this worked, it just did. To prevent this from happening in the future I installed another battery-monitoring program.
Thanks for your help!
P.S. I'd recommend trying this method for anyone having similar problems. Who knows, it might just work.