Forfeit the money on expired gift card

I have a R300 gift card that expired. I also have the original proof of purchase. It expired and Foschini said I now loose the money. Why if I have the proof of purchase do I loose the money. There are no dates on the card to say when it expires. Also nowhere in the conditions does it say you will loose the money after 3 years. I contacted Foschini call centre and they just gave me a date when it expired and said I now lost the R300. A cash card voucher is similar to cash. I do feel it is like *****ing my money, because you can see the R300 on the system on the card.