[@Guess Who] What's wrong with sound wave manipulation? I thought the disorientating effects it has on others would be a reflection of Robert's own clumsiness both mentally and physically.

If I'm being honest while I might not always be happy with the power level of Sapphire's semblance I think I sort of nailed it with how it relates to her personality. A girl that wants to shut out the world and never let anyone see the real her has the power to avoid being perceived.