Lending money to a stranger

Few days ago, as I was going to my colleagues house for a dinner invitation I was stopped by a man riding a scooter. He took out his helmet, and asked me can I help him. I wondered what can I do. Here is the rest of the conversation.

"Hey, I just need to buy some petrol from the nearest petrol-bunk. Can you help me?"
"Yes, I know the nearest petrol-bunk."
"No man. Can you help me to buy this much petrol?" he said indicating with his hand as if he wanted just a pinch of petrol.

I thought for a moment. I had little over Rs.200 (US$ 4) with me. In India, 1 litre of petrol costs Rs. 50. How much could I help him? Still I climbed on the pillion seat.

It was just 5 minutes ride. On the way I learnt that he had been riding on a busy road, when suddenly police stopped him and asked him for his papers. He did not have them on his hand, and had to pay quite a good sum as fine. Now he did not have even a penny, and will not be able to reach his home with the amount of petrol left in his scooter.

As we came to the petrol bunk, I handed him a Rs.100 note. He asked for more, and then I showed him my wallet containing the other one. Before taking leave he took my phone number, telling that he will call me the next day and pay me back. I trusted him and did not take his contact details.

I am still waiting for his call after 2 weeks.

I always try to learn from the incidents that happen around me. But I wonder what I had to learn from this one. Should I take the contact address from those whom I lend money from now on, however small sum it may be? Or should I stop trusting starngers with money?