Now that the cast has been officially revealed, I think the 6th team who makes it to Vancouver (and is eliminated) is James & Sarah. Based on their cast picture and the picture I caught of a team at Grouse Mountain (and the picture at Harbour Green Park, which I now believe are the same team), they seem like the only possible match. The top of Sarah's head appears to be level with James' mouth or nose, which is similar to the couple I spotted:
The only other male/female team that has a male with short, dark coloured/brown hair is Joseph & Grace but I had spotted them leaving Grouse Mountain before this other team even arrived. Plus, Grace's hair was braided when I spotted her.