i asked a local sheriff's aviation / sar unit official about this during a presentation two nights ago.
they have and use night vision eye wear. he said they've had lost hikers turn on their cell phones and point it in the direction of the helicopter. he said pilots have seen that illumination from "miles away".

i guess the point seems to be that seemingly little light can attract attention - but just think what a flashlight or dedicated strobe could do for you.