Something that restored my faith in humanity

So, I'm a waitress and this dude in scrubs comes in with his girl, gets some drinks and appetizers,( having a mini date I guess). When I go to close him out, his card declines. He gets upset, I had a good week in tips. figure he helps people and pay for it. He promises to pay for it(even though I say it's cool), writes his number down , tries to leave i.d. . Manger calls me an idiot for taking care of him and believing he's a good person. Three days later he comes in, pays off the bill (to cover me paying it) and then tips me this for being understanding. If you can't see -the bill was $35.36, he gave me $75.00 literally just for helping out someone I thought was in need. I'm still rubbing it in my managers face. People don't always suck.