Cat toys or human toys?

We gradually realised that the small human is not just benign, but bears a lot of resemblance to a kitten. He doesn't seem able to move very far by himself, but that's an advantage, from our perspective. He doesn't try to eat our food, and he mostly stays away from our toys.

So, on the whole, we've stayed away from his toys. They're not as interesting as ours, in any case.

Or so we thought.

We are particularly uninterested in books, which seem entirely pointless to us - other than when we jump on the shelves and pull them out, but the bigger humans don't seem to like it when we do that. So when the small human was looking at a book, we didn't take much notice until we heard a sound, and realised that this was no ordinary book. It had a little metal thing that went all by itself around a kind of track:

At least, it went once around. Then it stopped, and the big humans had to do something to a little knob on the side, and put it back. They called it a 'bus'. Of course that quickly became rather boring... the small human preferred to pick it up or move it, and so did we. We batted it around quite a bit, although the big humans kept putting it back. 

Most of the other small human toys were put away in a big and colourful bag at night time. I don't know why humans keep putting things away. It's a lot more interesting to have them scattered around the floor, under furniture or in the middle of the kitchen. That way, we come across things when we're not expecting them, which is so much more fun.

However, big humans seem to like things to be organised. The little one was happy to tip his toys all over the floor, however.  I thought I might check that there was nothing left inside the bag; then I had the idea of hiding completely.

I  have no idea how the humans knew I was there: