In the City of the Ghosts (Where is the Observer ?)

In this strange city therer was an Observer that must keep a very close surviallance of a gang, and it misteriously happened one night there was not Observer even behind the wall, nor in the cell phone system, the camera did not record a frame of his face, and all together became an stuff that exploit like virus.
Man's Investigation started a that exact moment. The Observer's task is what Man decided best fit to your plan to discover the exact location of that person. Walking down town find out by chatting people get used to working with this man from time to time and he always was the man that keep record of the movements in town. Said a bartender knew him that he always called whenever something happened. What nobody could answer is why the Observer stopped his work, disappeared as if the earth of the marcians took him. Why ? When ? Where ? ....