Why is a renamed custom template file still showing up in the template dropdown menu?

I recently renamed a custom template file, changing it from template-programs.php to template-program-schedule.php. In my template dropdown menu, Program Schedule shows up as expected, but Programs is also still there. I have cleared all caches and hard refreshed the browser, but it still shows up. I’ve tested the template dropdown functionality by creating dummy template files, which always appear in the dropdown menu after creation and then disappear as expected when deleted, but Programs remains in the list.

I searched throughout the whole website directory, and there is no template-programs.php file anywhere. Can a template listing be generated by a plugin or some other means without there being a respective template file?

How can I remove this template dropdown listing and/or track its source? Or, is it possible to flush and rebuild the template dropdown menu?