Thank you so much for helping such a sweet old kitty.
She sounds a lot like my Samantha who's 19 years old, deaf, with cataracts in both eyes and some arthritis and early stages of kidney failure(she looks pretty bony in her hip area).
Samantha will not respond to a loud clap behind her head either.
I think that this kitty must have gotten out by mistake and that someone is looking for her.
An elderly cat like that would not last long out in the streets alone.
Have you heard any update from the Humane Society that maybe her owner has claimed her?
Did you post any found cat posters around your neighborhood?
I hope this kitty finds a safe home.