The exess water? Well, some of it would have continued cycling around in the Guinea Pig's system because his body mass contains a lot of water just like ours does...but most of it got excreted in his urine. Most of the urine then evaporated into the surrounding air eventually, and you got to breathe tiny bits of it a year or two later, Bobert! ;-) Don't feel bad. You are breathing everyone else's spent urine too. Even George Bush's, in fact. It's the Great Circle of Life.