LE would have taken Mollie from the scene if she showed evidence potential, and returned her after processing. I doubt they would return her a mess, but who knows.
Just one example, it's not the hair, it's the saliva and hair:
"Missing Child Found Using Dog Hairs: The Murder of Danielle Van Dam
In February 2001, 7-year old Danielle Nicole Van Dam disappeared from her bed in San Diego. Her frantic parents didn’t know exactly when she disappeared—at night or early the following morning—and police had very little to work on.
Then a suspect slowly shifted into view—David Westerfield, who lived alone across from the Van Dam house. He was a meticulous gardener who left his house the morning Danielle was discovered missing. While other neighbors assisted in searching for the missing girl,
Westerfield packed up his RV and left.
Because of Westerfield’s suspicious behavior, police obtained a search warrant for his house. Inside, police found
dog hair similar to that of the Van Dam family’s dog
How Animal DNA Puts Killers Behind Bars
Prosecutors argued the dog hair was
clinging to Van Dam’s pajamas when Westerfield kidnapped her from her bedroom.
Westerfield was convicted of Van Dam’s abduction and murder and was sentenced to death on August 21, 2002.
“This is the kind of case we’ve seen most often, when we find a body wrapped in a comforter, sheet or tape, and there is animal hair stuck in the material,” says Lindquist. “The unique thing about animal hair is that dogs and cats groom themselves, so they are putting saliva on the shaft of the hair. We are more likely to find DNA [on animal hair] than on human hair because animal saliva is individual. Then animal DNA can be used as one of the pieces of the evidence puzzle.”
ETC