Variants of a mold are catalogued separately, so each one has its own sets and minifigs. Check these too if something you expect is missing here.

• 3081b Window 1 x 2 x 2 Classic, Extended Lip, Hollow Studs [no Glass] Sub-part of this part
• 3082 Window 1 x 2 x 2 Classic Glass Sub-part of this part
• 3081ac01 Window 1 x 2 x 2 Classic, Extended Lip, Solid Studs [with Glass] this part is a mold of it