If the Phobos-Grunt mission is truly lost, then professional and amateur groups will be modelling its orbit in an attempt to determine precisely where and when it might come down.
As with UARS, much of the spacecraft will burn up in the atmosphere; but any parts made of high-temperature metals, such as titanium or stainless steel, stand a chance of making it all the way to the surface.
Indeed, it is the fuel tanks that often survive the fall because their spherical shapes enable them to spin up and dissipate heat more easily.
However, the probability is that any debris would hit the ocean, given that more than 70% of the Earth’s surface is covered by water. This was the case with UARS and the German Rosat X-Ray telescope that returned to Earth last month.