Please call the FAA immediately if you suspect anything fell from an aircraft. You can find your local FAA Flight Standards District Office in the phone directory, or you can search our online directory at www.faa.gov/avr/afs/fsdo/index.cfm.
Please do not disturb the item, and take note of any overhead flight activity at the time, including type of plane and distinguishing marks. The plane’s registration, or tail number, is printed on the tail of the aircraft, and it serves as the plane’s “license plate.” If you can record it, that number will be extremely helpful. Please take note of any colors or markings on the aircraft. The exact time of day is also critical.
Seems it can come from a faulty toilet as pilots cannot dump in midair. So if you get the tail number and the plane is found to be faulty, I can't see why the planes owner isn't liable for damages.
So if you get hit with a chunk of blue ice I'd advise you to find a different lawyer.
Recently, an unlucky resident of Santa Cruz, California, received a special blue ice delivery courtesy of an American Airlines plane right through the skylight of his boat. He took the airline to small claims court and won a modest sum