I wasn't expecting a bug bounty, but not even a 'thank you' does hurt my soul :(
I totally understand how you feel though.
Or is there some weird loophole of "We didn't take action because of your message. We just happened to patch the same vulnerability after you mentioned it. We are not aware of any penetrations, because we didn't notice your message"?
Nobody knows.
But between taking an unknown legal risk, vs being seen as ungrateful, the choice for legal is quite clear.