Mystery of the missing photo!

[6demandingchildren]

I have a photo wall in my house, all the photos are of family and all are framed.
We went away overnight leaving our 16 year old at home but he stayed with his sister and only popped in to feed the cats and our home CCTV shows this.
When we returned a photo was missing out of one of the frames, we asked our son and he has no idea and didn't know what photo was in the frame, we asked all our other children and no one has a clue about this photo, after a few days I realised the photo was of my 16 year old son with our granddaughter that was taken a few years ago so both looked much different as they do now.
Not to drip feed there are around 60+ photos all framed, no other photos have gone missing and I believe none of the kids have taken it (they are the sorry of kids who would replace it with strangers)
While we were away the only person who came in was our 16 year old and he didn't go upstairs where the photos are.
This happened 4 months ago and it's still bothering me.
My questions to myself are,
Why would someone want an outdated photo why leave the frame as if they took the frame I probably would never of noticed
And by leaving the frame it was obvious it was taken.
It's really bugging me.

You say you have CCTV that shows who went in and out of your house, and only your son is on this footage, so it must have been him?

That's what we thought but when he was in the house he didn't go upstairs just into the kitchen then out the backdoor 3 minutes later

We have the nest system that has door sensors to show what doors are out I have been opened or closed and 2 cameras one showing the lounge and the other showing the hallway and stairs.

Did you watch the whole time while you were away? Could he have snuck in some friends through a window etc on a side not covered by CCTV?

I saw a few videos on social media where people sneak a picture out of a frame in someone elses house and replace it with a random picture. Maybe they only got to do part one.

You say you wouldn't have noticed if the frame had gone too so maybe it got knocked behind some furniture and the photo fell out and someone found the frame just before your holiday and put it back on top of the furniture?

When I was a teen left at home I used to do stuff like this all the time to fuck with my parents. I don't know why. Maybe he didn't like the photo? Maybe he thought he'd see how long it took to notice?

Might it have gone missing before that but you just didn't notice?

Possible but if so it would only of been a day or 2 but during that time only myself husband and 2 youngest son's 14 and 16 were in the house as I was isolating as I had an operation. So no one else came into the house at that time