People who don't know about the old Indian dogs frequently confuse them with coyotes, but the red coat is a giveaway - plus the dogs are more social and will hang around your house without killing the chickens.
There are rodents and canids a'plenty in that part of the park who would be interested and capable of making off with the long bones.
As late as this spring, coyotes had not yet been sighted in rock creek park, but they have been pushing into the DC area and are most definately in the surrounding counties.
There isn't any question that animals made off with at least some of her bones (notable example, the shinbone with the knobs chewed off.) The terrain (steep slope with creekbed at the bottom) would also be factor.