Yikes, good luck man.

That's actually really creepy...

Get out of the house now.

If you fully stretch your hand, you may notice your fingers somewhat curl, with your fingertips pointing away from where your palm is facing. This, along with the bottom corner of your hand (opposite your thumb) often being somewhat indented, can sometimes leave a hand print smaller than the hand leaving it, not to mention your hand print will already be slightly smaller due to its rounded edges. It's still a little unnerving, and if you haven't already, you may want to invest in a security system. Unfortunately, the world seems to be getting crazier every day.

that's because the fog made the hand print smaller. no need to worry

I say this with the most care in the world, make a movie about it.

That is the day that I live in a car

Have you recently moved in? Could be a non cleaned mirror from the last person. Or have you had someone over recently?

It could have been your own handprint that shrunk around the edges as the glass got fogged after the handprint was made?

That's a bit creepy but hopefully it's just a former guest's handprint.