Flags, DNA, Notes, Fingerprints
This phrase implies that there was no evidence or trace left behind of someone's actions or presence, particularly when they were attempting to be secretive or covering their tracks. It can be used metaphorically to suggest that someone has been very thorough in avoiding detection or leaving evidence.
It may take one to three days if you mean leaving it by choice. If you mean leaving it dishonorably, then it will be whatever time it takes for the Community Assistants to learn about what you did and take the appropriate action.
what does no evidence of security mean? what does no evidence of security mean?
It is unclear what you mean by an "official report". However, as an example, a police report would usually necessitate the presence of the police officer who completed it in order to authenticate it. You are advised to refer to the Rules of Evidence in your jurisdiction.
means leaving the work place.
If by leaving things you mean leaving material things and objects, he probably is getting closer to you and wants to move in.
What do you mean by leaving
It depends what you mean by "appropriate".
when is it appropriate to use arithmetic mean as opposed to median
she hates you
oral evidence is using your mouth and talking by using evidence
appropriate