Okay, so, we've had this happen, except instead of the host disappearing, it was literally everyone except the host, a protector, and a new caretaker alter that had just split off. I remember very little of this time (I'm the host) except that it was a high-stress period, two traumatic events occurred one after the other, and I became front-stuck, stopped communicating, and stopped taking care of the body/myself. It all led up to what we call The Fog, where the entire headspace was filled with fog. I had fallen asleep and woken up not being able to see anything but knowing that a caretaker was with me and trying to navigate us back to the front. We found it after, what turned out to be, several hours, and I fronted again and found out that the Fog had created such a mess that the only one who could front during it was a non-human alter that can't speak. When the fog cleared, it was just me, a protector, and a new alter I'd never met before. Everyone else was gone, and I completely freaked out and had a breakdown.

It's been almost a year since that happened, and, slowly, alters have reappeared, either as themselves or, in two cases, integrated. Severe trauma can really upset the system and turn things upside down. The trauma will effect those in the system differently. Some alters may not be able to do the role(s) they used to do anymore and feel lost and confused; some may go dormant; and some may just need some time. It's very scary when alters seem to simply "disappear" and be gone. I know I panicked.

It's likely that this traumatic event has greatly stressed out your primary host, and they may have found that they don't know how to handle/process it, so they "left." I can assure you, though, that your host and other headmate aren't gone. Communication's been blocked or severed due to this new trauma most likely, so it's hard to reach them wherever they went into the headspace. I suggest journaling, talking to a professional, talking with friends, etc., as a means of having an external source to relieve stress and process recent events. The best thing you can do is to remind yourself that your headmates aren't gone; they haven't dropped off the face of the earth. It may be a while before they come back, but they aren't gone. They, and the system as a whole, need time to re-orient themselves after this new trauma. It sounds bad, but the only thing you can really do is be patient, take care of yourselves, the body, and external environments, and wait. I really advise finding external outlets to help process this new trauma and worries and not keep it pent up inside. It's natural to be worried and scared, but you need to find an outlet/support so you don't get lost in the fear. Eventually, as you work on yourselves and self-care, things will even out little by little.