How to call Edge Animate's play function from external javascript

I have a symbol on the stage called "cart".... inside the symbol is my graphic that has a motion path put on it to the timeline (it is called "car_v1").

On my stage I have a code to hide the symbol cart with an external css class :

sym.$("cart").addClass( "hidden" );  ( this is the css - .hidden { display: none; } )

I have a function that calls an external javascript file.. from that external file I want to get the timeline animation to work:

here is the function called:

checkCar();

and here is the function:

function checkCar() {
if (AdobeEdge.countCar == 5){
AdobeEdge.getComposition("EDGE-172492634").getStage().$("cart").removeClass( "hidden" ); // this works!
AdobeEdge.getComposition("EDGE-172492634").getStage().$("cart").play(); //doesn't work!        <------------this is the line I need help with!

// sym.getSymbol("cart").play(); // this works inside of edge and the timeline animation runs!!!

}
}

Can anyone help me get the play function to work from my external javascript file? Thanks!

Kristen