I've been buying small beef roasts lately from Coles (the marinated ones).
I bought one the other day and popped it in the slow cooker earlier today. I thought it was a little odd that it had a few strings around it (like lamb sometimes does) but I snipped them off and popped it in.
Dinner time rolls around and I start carving it up and it becomes obvious it's a lamb roast (it's really fatty actually).
I really don't care for lamb. My DH will eat some later on though.
I still have the docket - would you go back in to Coles and see if they'll give you a beef roast to replace it? I don't want a refund, I'd just be happy with a beef roast of a close value.