Here's a rather interesting article on the topic: MYSTERY: NO pictures from first Ginsburg ‘public appearance’ since surgery?
Strange. At an event honoring Ginsburg, RBG was not even recognized publicly, and since RBG did not say a word at this concert, this makes her appearance all the more suspicious.
An RBG double who looked like her, but who could not speak like her, could have been present at this concert as there have been recent ads posted looking for someone to serve as Ginsburg's double. If a convenient excuse were to be offered for her lack of saying anything, it is well known that pneumonia/ lung cancer victims often have difficulty speaking for months.
Certainly, in this age of smart phones, one person could have taken a picture of RBG.