The rag disappeared from her hand.
Not long ago, one of my crit partners had a scene where she wanted to show a character being surprised by something. He was drinking a beer, and he was supposed to have been startled by his mother.
I suggested that she write the result rather than the action itself. When we're surprised by something, we don't notice what's happening, we notice what happens because of it—what we're holding hits the floor, what we're drinking spills down our front.
I ripped the sentence above from one of my WIPs because it's a good example of this. The character is thinking about something else, looking at something else, and she doesn't notice the person approaching her. Since she's the POV character in a limited third-person narrative, I can't very well write, "She didn't notice the person approaching." The fact that she's not noticing means that the narration can't notice, either.
What does she notice? When the rag she's holding suddenly disappears. Then she looks up and realizes that someone else has joined her in the room—someone nosy and bossy enough to just take things from her hands without greeting (which also went a long way in characterizing the second character).
The trick: make the object of the sentence the thing the character finally notices. In my crit partner's work, it was "Beer sloshed down my chest." He didn't notice himself jump, or notice his mother--his body reacted, and his response was to the result of all of that—the thing that finally actually caught his attention.