Just experienced the most bizarre thing ever on my Macbook

I had the Macbook on my lap and was browsing the internet while watching TV in the lounge - using my finger on the trackpad to control the pointer.

then after about 5 minutes the pointer disappeared... no matter how much I moved my finger on the trackpad no pointer would come up on the Macbook

But - my wife was sitting on her chair next to me with her iPad and complained that something weird was happening on her iPad.

I looked at her iPad while I was moving my finger on the trackpad on the Macbook and noticed the pointer was on her iPad and it moved when I moved my finger on the trackpad on the Macbook... How this happened I don't know.... I grabbed her iPad and went into settings to see if there was something in her settings that allowed this to happen, but couldn't find anything.... the pointer was stuck on her iPad and wouldn't / couldn't come back to the Macbook

I couldn't press any key on the Macbook either - it was like the keyboard had stopped

after about 10 minutes trying a multitude of things, I took the Macbook back to the computer room and plugged it in with the external mouse / keyboard and everything was ok.

I had a look at the trackpad settings on the Macbook and can't see anything there that would have allowed my pointer to go over to her iPad

does anyone know why this happened and how I can prevent it from happening again?