I would like to know how to find missing text keys? Sometimes when you change text key codes in the language area, they disappear from the search area. Where do they go...more so why do they disappear?

How can you find any missing text key?

I tried this but still no results for that key?
http://mysite.com/folder/admin/dev-tools/languages?&search=event+feed_add_item_label&in_keys=y

I'm looking for this key: {text key='event+feed_add_item_label'} in language area?

Wilson