Hidden homelessness is the experience of couch surfing. That is a good way to describe it. It's that sliver of time when youth in particular are doing everything they can to avoid being at home. That means spending extra time at a friend's house, which is how it may begin, sleeping in an extra room or on a couch, and potentially putting the need for a place to stay out on social media.
What quickly occurs is that the goodwill starts running out, the options become fewer and more dangerous, and the wrong people take notice and start to pay attention. That's when there's the greatest risk but also the greatest opportunity to intervene and provide whole-person support.