It was making a rattling noise as the pokey bits on the top made contact with the tire (while turning sharply to the right)
Would be my guess too. See if you can find two holes in your wheel well liner / wheel shroud / fender liner that are the same distance apart as the two little screws/bolts on your mystery part - then you know what it tore our of.
That is, presuming you still have a wheel well liner / fender shroud?
If no luck you'll probably have to ask your mechanic or the parts guy at a Toyota dealer.