I guess it's very YMMV. In October had a reservation that cost 280k points. Noticed on the way to the hotel that the reservation had been cancelled. I hadn't cancelled it and it was mid-afternoon so it wasn't like it was cancelled due to a no show. Long story short, I had to rebook using additional points to make sure I had a room for the night (fortunately hotel wasn't sold out). Hotel said they would fix but after a couple of weeks and no points returned I contacted Hilton. At first they said points had been refunded but that was because they saw some redeposits from some reservations I had made setting up the trip and didn't know exact dates, number of rooms needed, etc. Anyway, once I pointed it out to them I had my points back in ~24 hours or less.
So my experience was that mistakes happen but Hilton fixed it relatively quickly and easily.