Has anyone had a problem where one day they are working on a level and then the next day is deleted? It’s happening to me again. Had it happen on 4.8 and now 4.12, anyone know why or how to prevent it?
Have you checked the folder in your OS browser to see if the files are in there, and the engine may not be reading them?
In case you have more than one version of UE4 installed you might be simply doing the mistake of doing the work and next day loading it in the older version in which case the level won’t show up in the content browser.