I put "אני נמצא ילד." The middle word, I found in the hints with the other two. This was not accepted.
Nimtza is only for location
i'm in the house = אני בבית = אני נמצא בבית
the book is on the shelf = הספר על המדף = הספר נמצא על המדף
Maybe it was a glitch, you should report it.