Considering any hooker or anyone else for that matter, that knows they have HIV knows that they have to disclose their HIV status it's called jail time with fines. So no it was not a non-sensible question.
But what I mean is, it's a complete non-sensible question. What hooker in her right mind would admit to having HIV? If anything it would be extremely poor business practice. It's akin to asking an estate agent if the house he's selling is nice - "haha no chance! It's a pile of ****, surprised its still standing" asking a Prozzy if she's clean... "no I'm not. AIDS & syphillis last time I checked, now where do u want me?"
Doesn't matter who it is, it is always best to ask a partner about STD's and HIV.
I don't get the point of asking a hooker/escort if she is clean. She's hardly going to say "I'm absolutely riddled mate".
Test at 3 months for conclusive result.