If the pilot were approaching at around 130kts, could he or she recognise anything that small with any reliability? Imagine such a thing placed on the hard shoulder of a motorway, and you drive past at 150 mph, would you see anything at all?
Nevertheless, I'm glad to see the torch of scrutiny shone on these gadgets and their daft owners (what happens if they fly out of range or the batteries in the controller fade?). Maybe Captain Sully could do a lecture tour on handling the inevitable....