We should be able to look at see if the child has a data-react-id attribute but isn't rendered by this copy of React and consequently warn.

See https://groups.google.com/forum/#!topic/reactjs/mdwfKKJ0L2Q.

console.time(markerName);
  }
  var markup = ReactReconciler.mountComponent(
    wrapperInstance,
    transaction,
    null,
    ReactDOMContainerInfo(wrapperInstance, container),
    context,
    0 
  );
  if (markerName) {
    console.timeEnd(markerName);
  }
  wrapperInstance._renderedComponent._topLevelWrapper = wrapperInstance;
  ReactMount._mountImageIntoNode(
    markup,
    container,
    wrapperInstance,
    shouldReuseMarkup,
    transaction
  );
}
/**
 * Batched mount.
 *
 * @param {ReactComponent} componentInstance The instance to mount.
 * @param {DOMElement} container DOM element to mount into.
 * @param {boolean} shouldReuseMarkup If true, do not insert markup
 */
function batchedMountComponentIntoNode(