This idea is presumably based upon the notion that there is an even distribution of the relevant monopoly "tokens" across a given market.
Think about that a little - in terms of the potential prize liability for MacDs.
The normal way of controlling such (to all intents) lotteries is to have a few "golden tickets" capable of winning the more interesting prizes that are only dropped into the market in very small numbers - sufficient only to match the pool of prizes.
My experience of such marketing schemes (now rather historic I will admit) is that many prizes remain unclaimed - but giving them away was not the purpose of the exercise anyway.
Still the exercise was a worthy one - and it should be fun watching everyone looking for exactly the same missing tokens.