I did this at a Cracker Barrel once. I was at lunch with co-workers and I couldn't help but notice this couple, probably in their 50's. She was very ill - incredibly thin and weak and struggling with every bite. She was wearing a scarf over her head and had an IV in the back of her hand. He doted and worried over her - looking at her with such desperation and love.
I asked the waitress to bring me their bill when they were done (she was also serving their table). She burst into tears when I asked her to do that and she said, "God Bless" and then ran into the kitchen.
I wonder sometimes how they are and if she got better - I don't think I'd ever seen love so strong as I saw in that man's eyes that day.
And I hoped that the gesture made a small difference in their day. I left before they asked for their bill but I hoped that they didn't think I was calling attetion to their situation - only letting them know that people do care.