What should I do?

The babies are 12 days old today, they have been in their nest this whole time, Momma hasnt moved them at all. Except...the bedding was dirty looking today so I prepared some newspaper with paper towels. I put a blanket in front of the nest and gently put each baby on the blanket. I took out the old bedding and quickly put in the new fresh bedding, then gently put all the babies back. Momma went in the box and was nursing, I then left the room.

I came back 15 min later to give Momma KMR and to my surprise she moved them. She never has done that before.

She moved them behind the couch on top of some pillows I had back there. Should I leave them be behind the couch?

I hope they are ok back there, I dont see why they wouldnt be, there isnt anything dangerous in that room, but it worries me they are back there. Im also worried cause in the nest box/crate they were confined and couldnt get out, but now they could possibly wonder away.

What do I do?
Thanks!

She just probably moved them because she felt unsafe because of the bedding change.
They should be fine behind the couch, you could try moving them back to the box , but again mommy may move them again.
My momma cat moved her litter about 6 times, so i just gave up moving them back as i figured they were safe and she was happy.

Jada moved her kittens around the same time (about 12-14 days old). She moved them from the box to under my daughter's toddler bed. I moved them back and she moved them under there again. I tried moving them one more time and actually closing her in the room. She then pulled one out and meowed and scratched on the bathroom door to get out with the poor kitten still dangling from her mouth. She was getting upset so I just let her keep them under the toddler bed. They have been fine there although they are starting to wander out and look around. They don't get far though before Jada starts trilling and meowing at them dragging them back under. I'm sure yours will be fine there so long as there are no other animals in the house to reach them.