It looks like the Limited user access role is able to delete/change the folder location of a project they created through a form submission. This can be done by both click-dragging the project in the left folder panel and by clicking "Add to folder/project" in the project info panel on the right. Because the Limited user cannot access other folders, they can only remove the projects from the current folder, which causes their project to disappear completely.
As an admin, I can see their projects moved to the root folder because all folder information was removed but they don't have access to view projects in the root folder.
These disappearing projects are causing some confusion. I'd like to add an access role setting to disallow the removal of folders from projects. Thanks!