OGCFeatureGraphicOrigin

// get a point from view's click event
 view.on("click", async (event) => {
   // Search for all features only on included layer at the clicked location
   const response = await view.hitTest(event, {include: layer});
   // if graphics are returned from layer, get the layer id from graphic origin
   if (response.results.length > 0) {
     const originId = response.results[0].graphic?.origin?.layer?.id;
   }
 });