Hey if you have full coverage insurance then let them handle it...Putting the original filter on and playing dumb is just wrong...My friend's girl drove in a flooded street and had a stock filter but it hydrolocked it because the water was so much that it sprayed on and into the filter opening and evently got sucked up...So, it can happen with a stock filter. BMW was the maker...

 

Uh, am I missing something?
Flood damage is not a warranty item. I don't care what you do to the car before taking it to the dealer, hydrolock is freakin obvious and will not be covered in any way shape or form.
In my 9 years in the business I've seen my share of water damaged engines and none of them ever attempted warranty or received any. Claim it on your insurance.