Forgive me, since this seems like it should be obvious. Mine either fell off, or was pried off. As shown below. I found it, but it's deformed and there's at least one thing that snapped off that I also found. Clearly not going to just fit back in, but after looking it over, the inside looks like it has ridges to screw into, but the cap itself does not. Am I missing something? Or is that what they took?