I check the paperwork I didnt find the HPFP listed. Some of the fuel system was, injectors, lines. But, the first three linses of the warranty paperwork states void is cause by accident or abuse. I'm guessing they will say water in the fuel is abuse.Check the paperwork the HPFP is listed. Go there and pull your own fuel sample to have tested and if I'm not mistaken the Water-in-Fuel sets a dash indicator.
Part of why dealers try to push the blame to the customer is what you pay for the repair is sometimes almost double what warranty pays.