When I execute the following code:
var urlRequest:URLRequest = new URLRequest(\"http://somehost/with/some/path?andsomequerystring=true\");
urlRequest.method
It is because the way you are having your url. If you want to have your variables for POST method you need to use URLVariables.
var urlRequest:URLRequest = new URLRequest(YOUR_REQUEST_URL_HERE);
var variables:URLVariables = new URLVariables();
variables.andsomequerystring = true;
urlRequest.data = variables;
urlRequest.method = 'POST';
var urlLoader:URLLoader = new URLLoader(urlRequest);
urlLoader.addEventListener(Event.COMPLETE, function(event:Event):void{
trace('sweet');
});