There is a reason our house information includes "Please contact owner to show home". That means you are supposed to call and set a time to come by. I'm home just about all day since I work from home. Calling is a common courtesy that gives me a heads up that you would like to come by - it gives me a chance to make sure that I'm ready to show. (Which we always are)
That doesn't mean:
*Calling me from the driveway and asking if you can come in
*Not calling me and just showing up
*Calling at 6am to come by at 7am
*Calling at 6pm to come by at 7pm or later
However, the piece de resistance -
Not calling, showing up and coming in - it is not a pleasant thing to find out that, while I am standing in the shower, there are strange people coming into the bedroom. You are very lucky the dog (as small as she is) did not attack you. You should have had a clue that someone was home since windows were open, stereo in the bedroom was one and...wait, what's that? Water running upstairs?
Yes, I want my home sold. Yes, I want you to come by and show to potential buyers. But a little common courtesy goes a very long way.