if i were a real detective i would put my self in the shoes of the killer. I already killed the person so why stay there when the police comes up?
Some of y'all are NUKING this. The killer been left. If you killed somebody in a public restaurant are you really gonna stick around for the investigation? Hell nah.
Taking your assumption as the premise, wouldn't a women's restroom provide a perfect camouflage for a man to commit the crime?