you mention "who's done nothing to deserve it..."
There's a useful phrase,
No good deed goes unpunished.
Nowadays I'd punctuate it like this: No good deed goes unpunished :/
This is precisely what you say when you've done something trying to help someone else, and, by unlucky happenstance, you suffer because of it.
(It's rather like the outcome of "don't stick your neck out!" if you failed to listen to "don't stick your neck out!" :) )
For example, one time I was driving along and I saw an actual cliché of a pregnant woman, also with another small child, who was having car trouble.
I pulled over to help, topped my car, opened the door and ... scratched up the door of my nice car on a stone wall. Marvellous. "No good deed goes unpunished."
Another time - these things often seem to involve cars - I had just got a brand-new lovely car that day. Someone needed a ride to the airport, so I rushed to help. I managed to leave a work knife in the back pocket of my jeans -- ripped a hole in the lovely new leather of the driver seat. "No good deed goes unpunished!"
Perhaps this is what you're looking for?
If not, someone can downvote me - since no good deed goes unpunished :/