You were able to post in STH, so perhaps you had to switch to a non-mobile device to achieve this, I don't know. However, you should be able to see and reach all forums. They remain visible and available to everyone on all platforms (it wouldn't disappear from mobile and NOT from desktop at the same time). Of all the issues we have, this isn't one that we're aware of.
Can you explain more what you are experiencing? Any error messages?
When in mobile, do you know what style you're using (though, it shouldn't matter as styles don't hide-show forums). I'm trying to troubleshoot what's happening. It's hard to imagine someone not able to see certain forums that are otherwise visible.
Similar problem - haven't been able to access the Words forum from the mobile setting. I'd have to go on the full site setting. I'm using a free government android, but would also like to know what settings Specified deleted so I can try that.