Probably too late... But i'd melt it, then try to absorb/encapsulate it using Tapioca Maltodextrin. Then blow it out with canned air. (Or, more realistically, more easily then scrape it off.)
Only reason this came to mind was I was going to make some powdered Nutella to sprinkle on a Christmas dessert, but realized too late I didn't have the Nutella...
(Yes, I have made powdered Nutella before. Now, I need to go out and buy a jar a Nutella. And it gave me the inspiration to try powdered butter, should be a nifty way of buttering your toast! BTW, this is the only SANE use of Nutella. It's just TOO MUCH in it's original form...)
http://www.molecularrecipes.com/techniques/converting-high-fat-liquids-powder/
Don't blame me if it just makes it worse! Usually you get to powder by breaking-up what results, either by hand mixing, or using a food processor (best).
If the iPhone is actually unusable, you could use it in a "can it blend" experiment, and wind up with powdered chocolate to boot!
BTW, there actually is a dessert shop nearby called iDessert. I am waiting for them to get the letter from Apple's lawyers. It's not just the name - their logo uses the same typeface that Apple uses, and has an "app" icon shape!
As this is in San Diego, perhaps Apple is reluctant, due to the negative publicity received by Saks Fifth Avenue a few years ago, when they sued a local resale shop for trademark infringement. The name of the shop was "Sacks Fifth Avenue". It was located on 5'th.
