Deceptive offers on McDonald's app

I have downloaded the Mcdonald's app and started playing their games where you can win nice offers. I played it on Sunday 16 September 2018 and won a 90c burger and it showed that it expired on Tuesday, 18 September. I was going to redeem it at lunchtime on Tuesday but when I went on the app that offer wasn't there anymore but the other more expensive offers was still on the app. When I inquired as to why that offer disappeared they informed me it was subject to the availability of the product. There was no time specified that the offer was going to end. I am disgusted with McDonald's I feel they are deceptive and are just trying to entice the public to come buy at their stores with a brilliant offer but when you get to the store the offer is gone. I would not recommend their app to anyone and I will not be buying from them ever again