Fuel tank hose

Can you post a picture so I can see it? Not sure but I may be a vent one way valve.

I would think arrow end first, is it a valve can you blow through one end and not the other? I will let others look at this as I am not exactly sure at this point.

It looks like a gas can adapter that fell into the fill hose to me.

There should not be anything in that tube. I have seen anti roll over balls that are placed right where fuel actually goes into the tank. Were you having trouble filling the tank at the gas pump?

That is a can adapter like Ken mentioned. They hold the small flap open so you can add gas into the tank. Without them the flap stays closed and you cannot get gas into the tank.
Some sneaky folks also use them to run a small line into the tank to steal gas.

I agree with Steve and Ken, looks like it has been used a few times.