You're right. Small particles can exist in quite an ordinary sense. They can leave a trail in one spot, travel through empty space, then show up at a detector somewhere else, all in a predictable way. If you want, you could say they don't exist when you aren't looking, but you could also say that about the Moon, or your dog. Why would you?
There are circumstances in which "virtual particles" can be converted to real particles, ones that can travel around, by various probes. For example, strong electric fields can pull electron-positron pairs out of the vacuum. Maybe somehow that sort of effect has stimulated Chopra's literary imagination.
By the way, even the point that one only sees the little particles by the traces they make is not particularly distinctive. The same is true for the Moon and the dog. It's just that certain sorts of traces (some patterns of light on our eyes) are so familiar that we feel as if they are direct experiences.
(published on 05/24/2012)