It is not uncommon to wash certain metallocenes (Cp2Fe, Cp2TiCl2, etc.) with conc aq HCl to remove the assorted cats & dogs that might be present. A few of them are considerably more hydrolytically stable than one would imagine. Typically, long term acid exposure is to be avoided. Without doing a lit search I would agree that the Fe (3+) species is a good guess. Some metallocene species form oxo bridges on exposure to water. I've never heard of ferrocene doing it though.