2005 Ford Escape Fuel Pipe Flapper Valve Problem

Sorry for the repeated post, but my Laptop Keyboard skips resulting in
a lot of typos

I have an 05 Escape and noticed that the flapper valve is missing in
the fuel filler tube. Not sure there was one there to begin with.
Should there be a flapper in the filler tube?
I know this sounds like
a dumb question, but I never noticed if there was one there.
If the valve broke off, it would probably be stuck in the tube and
maybe the reason why it is extremely difficult to fill the tank.