I seem to have run into the same problem you did, but have thus far been unable to find the solution. Mind sharing your method?
Go all the way down where all the copyrights are
In the last line you should see " Mobile style by Dartho" and "Default style"
Click on "default style" don't change the page it's only applied on this specific page Now go all the way down again
In the gray area on the left there's "contact us" "Arlong park" "top" and in the right there's a box to choose theme. You might think you are in retro theme already. You are not. Pick a theme. Now all the page are normal again and you can go to settings to set the theme you want permanently.