What does "[something]'s up on the cloud" mean? Is it an idiom?

Native speaker’s answer
Rebecca
It is an idiom! The common phrase is someone's "head is in the clouds". If one's "head is in the clouds", it means they are disconnected from reality. They daydream a lot and live in their imagination. It's said as a criticism since they can be unaware of what is happening around them. Ex: Sorry, I had my head in the clouds. I'm listening now. Ex: Julia's head is always stuck in the clouds. Ex: You got your head in the clouds? Pay attention!