Templates disappeared from Elements tab

The white triangle is missing from Templates in the Elements tab (see screenshot) so I can no longer access the templates from within the manager. I am assuming they are not gone from the db because the site is still clearly using the templates.

Tried both Chrome and FF - current versions. Tried clearing the cache in manager and also deleting the core cache folders. Tried a hard refresh of the browser.

Immediately after deleting the cache folders and logging back in, the triangle flashes for a moment and then disappears. Hovering the cursor over the spot where the triangle should be changes the cursor to pointer but clicking does nothing.

This site is on Revo 2.2.2 pl advanced.