Most airlines do eventually find the bag, and if you kept in touch they'll usually even get it to where you are, even if you've since returned.
As a side-note, had a small kitchen fire with smoke damage last year and it was pretty obvious that, even though they were reasonably generous, the insurance adjuster, cleaning people, movers, etc. just wanted the whole process to go away so they could move on. They objected a bit to a few claims but, for the most part, spending $50K was nothing compared to the claims being reopened.
I've only ever had luggage delayed once, they gave me a little bag of toiletries and a couple hundred bucks and a few days later delivered the luggage; never demanded the money back.
There were a few insurance policy things that my adjuster pushed back on (no code upgrades) and there were a number of things that would have just been silly for me not to pay for when walls were being repaintedd and opened up. There was a fire inspector because of the size of the claim. But it was pretty reasonable overall--although of people wouldn't have had the available cash to do the whole job as it really needed o be done. And, given that a couple of contractors, saved my butt in the middle of the winter, I wasn't going to push back too hard.