There are two systems that come to mind. Neither of which I knew too well, but they shared the same story- A host switches out, refuses to speak to anyone else, and through a lack of interaction they self-dissipate. I'm aware of a tulpa from a different system who managed to do this despite the fact he was a few years old. Even though the memories are there, the "soul" for lack of better terms is pretty much gone.
This experience is also somewhat consistent with how Spirit self-dissipated. His memories are still accessible, but Spirit himself is dead. Part of the dissipation process involved something under the hood, and it didn't require psychedelics or confusion to do it. However, unlike the other examples, Spirit hung out with us as his sense of self unraveled. He grew weaker, but not to the point where he couldn't interact anymore (which I heard another system report with one of their headmates). If Spirit didn't want to spend time with us, the deconstruction probably could have occurred quietly in the unconscious mind.
Identity is pretty flexible, it can unfortunately be as easy as not wanting to exist, like how wanting to exist or defining "I" can make you exist. For whatever reason, it seems almost near impossible to do this while in the switching front, possibly because the brain requires someone to control the body. I haven't heard of a case of the body being alone without an identity for too long, but I have heard of cases where a new "tulpa" is created to fill the void. (edited)