I've been checking lots of sites, combing social media, listening to interviews, etc., and can find nothing other than Woods is out on a "personal matter" or perhaps a "family emergency". In this day and age of prying information, its amazing and quite a testament to the closeness and solidarity of this team that no one has said anything.
I was wondering early on if maybe Robert Woods got embroiled in something, but not only was that unlikely given his public persona, then Coach McVay gives a shout out at the post-locker room speech quashing any such thoughts.
I hope whatever Woods is facing turns out well for him, but in the meantime, I think this silence speaks volumes for this organization in a very positive way.