Of course, it seems like terribly bad police work to tip off the person that you're watching, to let them know that you're watching them. Because then, if they are terrorists, they're just going to be more careful. You want them to be SLOPPY, not CAREFUL. If they're actual terrorists, letting them know you're watching isn't going to suddenly stop them from being terrorists. If anything, it's just going to piss them off more.
Again, TERRIBLE police work. You can take a picture of the picture without tipping off the suspect. See also: not leaving shit exactly where you found it (the bags moved out from the wall), especially in a nearly empty apartment where that is exceedingly likely to be noticed.
The connection to Ramadan seems tenuous here though, at best. I have a feeling that REGARDLESS of when he was travelling, if he had opted out of the pornoscanner and set off the explosives detector, the result would have been the same.