Last week I lost something very expensive. I looked all over and could not find it. I went back a few times to where it was lost to see if maybe I missed looking somewhere - under a bush, under a bench, etc.
Last night a teenage boy calls me up and tells me he found it. He heard from somebody that I had lost the item and was looking for it, so he looked up my number and called.
He saved me a very big expense I would have had to replace it, yet he refused a reward.