I put "Etek ayakkabında" and got it wrong. I'm trying to understand why. Is it considered an incomplete sentence? Or maybe it just doesn't work that way grammatically.
I guess I thought of "Etek ayakkabının üzerinde" as more literally "The skirt is on top of the shoe."
Simply consider it as a rule: if you want to use such location indicators (üzerinde,içende,üstünde..etc) after a noun, then you must add (-in) after the noun that precedes it. (Noun+in + locative).. Consider the vowels harmony of course.