IMO That doesnt make sense.
You question why he would leave? Possibly because he just killed someone and doesnt want to be caught?
Why would you flush clothes?? You can easily hide those in a bag or garbage.
Why would you flush ID? Well you dont want to be caught with someones ID do you?Especially not someone you just killed. And as well a phone these days is almost a form of ID
Most killers are, aside of the fact, they are killers, also human beings. Human beings watch TV which in our days has led to every unsub knowing a lot more about police allegedly works. I've observed in other cases, how this "common TV knowledge" worked out.
This guy kills Elisa, but not on the roof. So he has her probably in his room. Does he panic? No! He waits for the night and brings her up and stuffs the body in the tank. That indicates, he was not in panic. Now he has several options. Lets look first on the when to leave problem:
- He can run. But he can also guess, that LE will look for everyone who left Feb. 1st even when the reservation was longer.
- or he can stay till the time his reservation ends and very normal leave the hotel. Which doesn't mark him as suspect and he can basically hide in plain side.
So, instead to get an APB to be questioned on his nack, he just sits out some days and can go his merry ways without any questions asked. And after he is out of LA, nobody knows anyway that he was there. Latest two hotels later nobody who meets him would even come to the idea to ask him whether he was in the Cecil in LA. So, as long, as he can hold his nerves together, he can only win by waiting for the end of his reservation. That is, if he isn't lucky enough to have booked there only till Feb 1st in the first place.
Now the same for the cloths. Ha had to assume, people saw Elisa and may remember the clothes she wore. He maybe even can conclude, she was with those clothes on some security images. He can't put the clothes in the tank with her. Every CSI watcher "knows", clothes hold all kind of fibers including spores of the one plant that in the whole world only grows next to his room door in the Cecil. It'S not how the real world works, but thanks to Jerry Bruckheimer, a lot of killers think that way about such details. So, he has to destroy the clothes, he don'T want to leave them behind he don't want to get caught with them, he has to destroy them. Options?
- burning. Causes smoke detectors to react unfriendly
- put them in a garbage can. Well, in TV, police does a lot of dumpster diving. He has touched those clothes. No way, he let a dumpster diving cop find those things.
- rip or cut them to pieces and flush them down. One by one. He can do it in his room, no potential witnesses, nothing to save from dumpsters.
The problem is, he can't do that with anything made from plastic. Credit cards, IDs, and of course, cell phones. He has a problem with that. The other problem is, he is too cold in his decisions. He is not panicking, he shows no signs of remorse or disgust. Lets hope, he didn't enjoy it so much that he keeps for example the cell phone as souvenir.