Weeeeellllllll !
That happened more than once - with and without lols or lolz.
But there are quite a few other, known, unknown or anonymous friends or strangers, who's help or support went unnoticed, and to whom we could not say thank you.
So, if thinking of them, when facing ungrateful people, no "good deed" is useless - even if it "doesen't go unpunished".
And sometimes, a respectful bow, a handshake, an awkward, happy smile or an acknowledging nod is better than a disdainful or condescending "thank you".