I have a feeling, there is someone in Rey office who tried to help him by telling him to run away from someone and hide. Not sure what information Rey has but its something big and thats what was bothering him. Those alarm could be break ins attempts to his house. That note might have key to some documents or something which is what Rey was hidding. He might have ran off to the nearby hotel to hide himself. The time of phone call and ticket in parking lot could give us time between when he actually parked in hotel. Also time of death could conclude if he died on same day he went missing or he rented a room in the hotel and stayed. Was the rooftop open for 8 days? If it was not open then theory conclude he rented a room and when someone who tried to kill him.he might have tried to go out of the window to hide and slipped and fell hence the broken flip flop. Now why the phone is not broken or glasses? Did someone did a sloppy job in the hotel to save hotel reputation? Check the entry details for the people who stayed in that hotel from day of missing to body found day and call everyone in list, if someone name or number doesn't match that could be Reys alias which he was using. There is someone in hotel or killer tried to coverup by placing the Mobile and glasses unscratched near by body and closed the door. That was sloppy job. Also cctv is disconnected means they don't want to know who else was their in the room. So check all the room which was covered by shutdown camera angle.