Uninvited guest

June has been a mostly uneventful month for me, still little work to be found for freelance, but three incidents occurred during the past few weeks, around midnight each time, a visitation, of sorts.
It started on a date I'm unsure of when I was in the kitchen with a roommate, Luke. My friend, Ty was in the living room at the time. While we, Luke and I, were talking we heard a call from the living room, just down the landing.
"There's a bird in the room."
A bird? Luke and I went down the landing in time to hear our friend call again.
"No, it's a bat."
A bat. In the living room. No idea how it got in, but there it was, circling the living room. And there we were, three grown men, staying low enough that the frantic bat didn't collide with any of us.
While we tried to figure a way to get the bat out of the house, Luke decided to turn off the lights, open the front door and whistle. And sure enough, the bat made for the front door, following the sound.
And that was it, the bat flew away and that was the end of it.
For one night.
I couldn't figure out where it came from. As far as I knew all the windows were sealed, and the chimney was closed so it could not have come in from there.
A week or two pass and again around 2:00 a.m., same time as last, the bat appeared again. This time it clearly came from up stairs. So we knew for sure that it wasn't coming in from the chimney. This time, in Luke's absence Ty took up the same tactic of turning off the lights and whistling at the front door. However we weren't entirely sure it passed though the threshold of the door, since it was to dark to be completely sure.
Either way there was no longer a bat flapping about the living room, so we called it a night.
The third visitation happened a few days later in much the same way. It has started to become something of a routine, apparently for the bat as well. All we had to do was turn off the lights in the living room and open the front door and it made for the front hall.
Although it would fly around the front door, it seemed reluctant to, or unable to pass though the front door my itself. Ty again whistled outside and eventually it flew away. this time we were sure to close the door after seeing it leave.
Hard to say if that was the last we will see of the bat, my other roommate, Amanda, has affectionately named Hershall. In a way I miss it, it was an exciting change of pace, although I guess it's also nice to not have to worry about colliding with a bat when walking up to bed after 2:00a.m.