There's a bad glitch with the sled, thus making you stuck. And unfortunately I can't remember what I did exactly (it was late last night) but there's two scenarios that either happened.
One, I didn't grab the sled (because I assumed Bill was going to) and moved to the next screen. When the sled wasn't on the ground and I tried to go back, it was gone. (I think this was the one I did).
Or two, I did grab the sled but then picked an item from my inventory, trying to do something with it, and the sled somehow just vanished from my inventory.
Either way, I request that you add a "new game" option because I am completely stuck. Every time I refresh the page, it loads the game right where I left off. I did finish the game on your website, but I wanted the medals on Newgrounds. :c Anyway, it's a fun game. I'm really enjoying the series.