Bats in the house?

Moving between houses creates a little extra work.  Before we leave we drape covers over the furniture which then of course have to be removed when we return.  We also have to turn on the heat, the water heater, plug in all the appliances, start internet serve just to mention a few things and of course the general cleaning to get rid of the dust build up which in this case was seven months worth.  These of course are just the norm and we are getting accustomed to it.

Monday night however while I was working on my computer in what we call our library, Eileen walked in and said what is that smell.  I got up to see if I could smell what she smelled and it was a hint of dead animal.  We looked around but could not come up with a source or definite type of smell.  Tuesday morning there wasn't any trace of the night before.  That night Eileen was in the library and I came in and the smell hit me.  She was sitting down like I was the night before and didn't smell it so I looked up to see if there could be anything high causing the smell.  It immediately hit me the smell was coming from the torch lamp in the corner.  I looked into it and sure enough this is what I found.

They say bats can get through the smallest openings and I guess an empty house was inviting.  Anyone have any ideas how a bat can get into a tight house - all the doors and windows are fairly new.