Probably not, but what is your warrenty, and to what extenet is rust covered? The hitch reciever is easy to paint. Better than having all the fasterners rusting away like on mine.
The hitch most likely won't be covered. Usually only the sheet metal is coveraged against rust perforation. But you can always take it to the dealer and see if they'll do anything (beside Toyota is down now), worst they can say is "no."
Body rust repair is not extended with the Platinum coverage. And the hitch probably isn't either (mine was pretty bad too. Used a rust coverter... all better.) But it can't hurt to ask. I had rust on my rear lift gate at 55,000 on my 07 and they repaired it last week as a courtesy repair. I think most dealerships realize certain areas rust faster than they should and they may be more willing to do it. And these says they need all the good PR they can get.