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.

• 2377c01 Window 1 x 2 x 2 Plane with Glass this part is a sub-part of it
• 2377 Window 1 x 2 x 2 Plane, Solid Studs this part is a pair of it
• 4863 Window 1 x 4 x 2 Plane, Solid Studs this part is a pair of it