How can a hub no one has read have 3 reads?
Well, *you* read it.
I'm not an expert on Hubs by any means, but I understand a thing or two about the Internet. Web pages that track hits or views usually do so without discrimination. If you edited your own hub a couple times before deciding to delete it, it's possible it tracked you visiting the page and counted it toward the read total.
Other than that, there are a few users out there who like to read the latest published info. If you published it before it got deleted, it's possible someone else viewed it before the delete happened.
I don't know much about the situation in particular that spurred this question, but I think one of those two possibilities are most likely. It could also be a random glitch, but it's less likely.