I've always believed that what comes around, goes around. If you treat others with respect, then you will get it in return. Of course, there's always the arsehole or two that only think of themselves and be damned with the rest of us. Eventually, they get what they've been dishing out to everyone else. I think you could call that "poetic justice" as well as karma.
In your situation, you did a good deed for someone that you've never even met, and in my book, that's a very noble thing indeed. Unfortunately, there just aren't many people in this world anymore that are willing to do things like that. That's not to say that nobody would, but it's getting rarer and harder to find anyone that would.
My hat's off to you sir, congratulations and thanks. I wish there were more people that would take the time to help out someone else in a time of need. But on the other hand, I can also understand someones reluctance to try, because of the number of people that are hurt, robbed, raped, or killed by someone that they had stopped to help. It's a rare thing percentage wise, but it's the perception that it could happen to you that keeps a lot of folks from extending a helping hand. It's like that old adage, "It only takes one bad apple to ruin the barrel".
Keep up the good deeds TDLB, and God bless you.
