He hid it on top of the shelf unit a while ago I think shortly after he first started abusing her. Maybe above the cupboard where the dress was, but maybe on another shelf. He did see her adding something to the suitcase recently, when he was in the cafe, that's why he went through that charade with his "special marinade bowl". I did ask a while ago, why she never found it dusting, but perhaps she does not do the top of the shelves and he would not want to point this out to her. We have not seen him checking the camera too often, although presumably he must do so or his phone would run out of memory. Problem with surveillance is that it it is time consuming to view. This is just another example of the lack of thought about detail in this "drama".