I think you could manually move the layer around so that it's the last layer. Another option would be to set the opacity of all other layers to something like .5 so you can ensure that you can see through them at least.
Here's how you might approach the first option:
var map;
var myFeatureLayer;
var query;
myFeatureLayer.selectFeatures(query, FeatureLayer.SELECTION_NEW, function(event){
if (event.features.length>0){
map.reorderLayer(myFeatureLayer, map.layerIds.length - 1);
}
});
When the features are deselected you may want to change the order of this layer back to where it was previously.