Content type disappears in content list
Suggestions:


Make sure the module handling custom node type exists and is enabled.

Based on case_studies_node_form callback, it's most likely case_studies module.

If you don't know type of the node, you can load it using drush, e.g.

drush ev "var_dump(node_load(123));"

Make sure the module which handles custom node type defines hook_node_info() in its .module file.
Clear caches (drush cc all, restart Memcached/Redis if present).