The Curious Mystery of the Amazing Moving Shoes

When I was a little Debra, I loved reading Nancy Drew mysteries, and now that I'm all growed up, I'm addicted to Criminal Minds, House, CSI - I just love me a good mystery. Now I have a real-life mystery, and I can't figure it out.

Ever since Ava came to live with us (on Sunday) something weird has been happening. Every afternoon, when I come home from work, there is a shoe placed somewhere in the middle of the floor. One shoe. One of MY shoes, from MY closet. The shoe isn't chewed (if it was, I would blame Frankie for sure) it's just...MOVED.

One day it was a ballet flat. Another day it was a heavy biker boot! Yesterday it was a strappy heeled pump.
I'm assuming it's one of three furry unsubs who have access. I do not however, have a motive, and I lack evidence. Katie has never done anything like this. so while she could do it, it would be a new M.O. for this suspect. Frankie has, but it was to rip the shoe apart, not just move it to a different location, so she's a suspect, but it's not her signature. Ava is REALLY little, I don't think she COULD drag a biker boot three rooms away, and she's not shown any interest in the closet or my shoes, in my presence.

So I want to know:

Suspects Flee Scene of Crime

WHO is doing it?  And HOW  are they doing it, since I closed my closet except for about 4 inches (because Katie likes to lie down in there). But Most importantly, WHY are they DOING it? The mystery continues. I will let you know what is left for me today....(insert creepy mystery music here.)