Reuse Head Gasket??
Like BJR said because the gasket hasn't been heat cycled it will most likely (99.9%) be fine, but head gaskets are cheap compaired to the trouble of having to replace it in the car if it doesn't seal. If it were me I would put a new gasket in it because I am not a gambling man and seem to have rotten luck at this kind of thing, but that's just me.
Chuck