Special not honoured

I bought a packet a packet of nuts and raisins, when I got to the till, the cashier tells me there is a special of R100 for 2. I leave the till to go and get the second packet. When I get back, she rings the two items and the special does not register. She calls a senior for authorisation and it turns out the special has expired. Was I not still entitled to the special? Is this not similar to when an incorrect price is put on the shelf? Should the store not have honoured the special? I was at the Mall of Africa store on Saturday the 11th of January 2024.