If it's not under pressure, the
oil on the other side of the filter media isn't going to just run out. Leave it upside down for a while in the drain and it'll mostly drain. If the bypass were open then most likely it would all run out.
Or are you worried just because the filter didn't actually hold a whole quart? If that's the case just spin that baby back on and stop worrying. they never do unless you are using an over sized filter.
Steve