Yeah, that is not a good sign that youre not showing for your primary brand terms (assuming that there is no user intent overlap with generic terms, or that there has not been signifcant news about your brand,etc)
Are backpages still ranking for anything or have you disappeared completely?
RE:"The page is showing 'officially' in google but also not for any of our other decent search terms. Other pages are showing instead, so there isnt a 'no index' tab on it."
Is this your homepage or a backpage that you're referring to?
I would not look at DA...that is a third party metric, so it will really not help you with fixing the issue.
How much link build have you been doing, was it a really aggressive campaign? DA is not a good proxy for the links, google is way more sophisticated in how they analyze links?
The easy culprit would be links BUT I'd need to know more about the features of the links to be able to say for sure...one thing that comes to mind off the bat is do they have keyword anchor text? Can comment more on the link work you've been doing?
Have you made any recent changes to the site? Parhaps a recent deployment affected how you appear in google or have you already taken a peek at that?
In addition to links, have you guys been tweaking anything on page?
Anyway, I'm sorry to hear about the issue...I've seen stuff like this before and the best thing to do is go through all the possible culprits through a process of deduction to try to isolate the issue...happy to comment more but need more info..
"...using this: sages act out of constructs but they do not rely on them"