Fan down, FAN DOWN!

So I have this tall oscillating fan that I use to move the AC air around the house. I either have it blowing into the living room, or down the hall towards my office ( the AC is in the Dining Room).

Well, its been on for a few days, so I shut it off last night. Big mistake.  Now its making a horrid grinding noise when I run it.  So i took it apart to see what I could do, as I’ve to dismantle and clean cat hair out of this fan before.

First thing I noticed is there’s a piece missing that literally holds the fan blades onto the thing!  I have no idea how or where its gone.  And I know exactly what the piece looks like, as i’ve dismantled it before so it isn’t like i’ve misplaced it. If i saw it, i’d know what it was!

I have no idea where its gone.  I’m also confused as to how it got out from inside the cage around the fan blade, which was properly closed.  Maybe I have gremlins….