It is my understanding the reason they couldn't confirm it was her right away was because of how badly beaten her face was. Apparently it was so bruised and swollen that her facial features were unrecognizable. So horrible
Body condition: There was a question, when she was first found, if the body was indeed Mackenzies. This would indicate that authorities were unable to identify her by just looking at her.
If she was placed at the Crescent Bar location on Friday or Saturday, the only reason they would not be able to identify her, is if something was done to her to prevent identification. In addition the police, if they started testing immediately, would be able to tell if she was at that location for more than 36hours.
If she were placed at Crescent Bar on the night that she disappeared, the condition of the body would have been in the second or third stage of decomposition. Considering that she was found fully clothed, feet in water, and somewhat covered, decomposition could have been delayed.
Temperatures that week ranged in the mid to upper forties. This could have slowed decomposition as well as preventing insect infestation.
The third option is that someone kept her in cold storage for a period of time, before the placed her at the site.
My opinion is that she was placed there near the time of her disappearance. This would explain why it took so long to identify the body. The body would have looked as if it were bloated which could have been confused with black and blue. In addition, the warmest day that week was Saturday. This could explain why it took so long to find the body. It was the only nice day that week for a walk on the beach.