There is a more simple method which use all standard functionalities.
Just create a category and sub categories. for example the main categorie is "Photos" and the sub categorie is "Photo Albums". Your K2 items are assigned to the "Photo Albums" categorie. Then you create a menu for K2 Category "Photos" which will display also the subcategories so you will be able to see your items there. then assign your module to "Photos" only. You will see your module only there and not by viewing the item.