If you and your girlfriend are healthy human beings? then forget it and just put it to the back of your mind, unless you a freak like Jerry Seinfeld.
Good Luck
I guess it is possible if you were leaning forward and your legs were open some when the toilet water splashed up. I wouldn't worry about it, but if you develop any new symptoms I would get checked out.
Did the toilet water hit your face or your bottom? Maybe when you washed your hands you got your mouth wet. It isn't likely it would splash that far. Even if it did which I doubt, it is very unlikely to get ill this way. I don't believe there are any reports of this nature that one got an illness in this manner. I wouldn't worry.