見落とす
みおとす · miotosu · JLPT N1 · verb-godan
to fail to notice
見 (see) + 落とす (drop) = sight that drops right past the thing without catching on it
落とす also means to lose or let fall, as in 財布を落とす. 見落とす is the gaze losing the item on its way past. Compare 見逃す, which is closer to letting it slip by.
落 — grass radical 艹 + 洛 (water 氵 + 各)
Originally written with the grass radical 艹 over 洛, depicting leaves falling from plants. 洛 serves as the phonetic component (giving the luò sound) while 艹 supplies the meaning of vegetation. The sense extended from 'leaves falling' to the general meaning of falling, dropping, or settling down.