Man, I'd be worried to the point that I'd probably replace all 20 studs. It would bug me until I did.
Whoever thought 5 lugs was better than 6 at Toyota should have to replace these for you. Not that a few percent less load on each can solve a numbnut overtorquing, but losing two of 6 would worry me less.
'91 Pickup - Imelda
'08 Tacoma TRD - Donna