Previously, I had mentioned that there are two main genes that cause hairlessness in the domestic dog (and other canids, should crossbreeding occur). One of these is the dominant hairless gene which also affects dentition. It was discovered to have originated in Latin America. The other does not affect dentition, but it expressed from a recessive gene. It occurs in the American hairless terrier. That breed came from a hairless puppy that popped up in a normal rat terrier litter in Louisiana. (Rat terriers are an endemic American breed of terrier.)
I have stumbled across another hairless dog. This time it is a retriever. Not only that, it is in a retriever that originated in the United Kingdom. It turns out that there is some patterned baldness in the curly-coated retriever, which has a very strange coat, even its normal form. It is very short and tightly curled, unlike any other breed of dog.
The patterned baldness in this breed is not well understood, but it is not as extreme as is in the breeds of hairless dogs or the hairless coyotes. This breed is quite rare, especially in the US, so I doubt that this breed could be a source of the blue dogs.