Hi Julie,
How old is the dog? If it's an older dog, it's likely that it could have been hearing and gone deaf. That happens in many breeds. If it's a young dog, it's probable that it was born deaf. There are breeds that do have tendency towards deafness, but I don't know if CKC's are known for it.
I've lived with two dogs that went deaf in their middle to later years. It's really not much trouble if you start incorporating hand signals and not startle the dog when its back is turned. Waking up the dog out of a deep sleep should be taken carefully. I used to blow gently on Pepper until she'd wake herself up. Always woke with a smile on her face too :)
Keep an eye out for eye sight degeneration too...sometimes hearing and sight problems accompany one another. The first sign can be difficulties going from a lit area to a darker one...hesitation and confusion where the dog is going to step next. The eyes aren't able to focus the change in light that well.
hth
toodles