Just cause I don't know, but what kind of extinguisher was it (Dry Chemical (or an ABC rated extinguisher), Carbon Dioxide (or BC rated), or water (class A).

If you have a red extinguisher, it's most likely a Dry Chem or CO2 cylinder, so unless you have a water trap or have the extinguisher mounted near a heat source, you will need to make sure that no moisture gets into the cylinder, since the ABC and CO2 cylinders, while stainless, really like to rust up.

Of course, if you taked to the "fire guy" about it, I'm sure you'll be fine, but just in case others were now thinking about this as well, using one of those cylinders (especially an older one, which is what most people will come across) could possibly pose a hazard down the road.