I'm sure there is a way for it to hold the themes.
I've found that my phone holds my old theme choice (for the phone), even when I've reset it for the computer. It may be down to the way it caches things. A few other people have mentioned the themes not holding (which I experienced at the start as well), and changing the current theme to 'Elliquiy 2' on the look and layout page, before clicking 'change' and choosing the specific theme for Elliquiy 2 is what solved the problem.
You could try removing the Elliquiy cookies or refreshing the browser (Ctrl-f5), if that doesn't work (or Shift-Reload on a phone?). If changes are made to a theme, you need to do a forced refresh (Ctrl-f5/Shift-reload/Ctrl-reload/or Shift-f5) in order for the same theme to change (to an updated version) on your own system.