Mystery piece fell off my van??? pls help identify?

Sounds like the charcoal canister used to recycle the gasoline vapours from the gas tank. Usually under the hood on the penger side, towards the front/radiator. One of the hoses comes up from the top of the gas tank, and the second one goes from the canister to the intake manifold of the engine. If it is the canister, there should be the two hoses loose in the engine bay. If you find them, they both should be plugged, if you don't return the canister.