Flanker, I appreciate it's disconcerting. A similar thing happened to me a few weeks ago after I'd joined downwind for 23 (with broadcasts) only to have a Jabiru blast off from 05 as I was late downwind. (In this case the element of the ambo and the level of expected professionalism was, of course, not a factor). The Jab was RA Aus registered, but I don't know that I'd draw any conclusions from that. I believe that the pilot probably had a fault in his receiver, or had the transceiver volume turned down.
The saving grace was that he did at least give a taxi call (of a sort) but after that it was pretty poor - accepting that I was hard for him to see, he also missed other ground traffic taxying for 23 and taxyed onto the strip without pausing. With a bit different timing, he could have met me head-on on my final, or could have met a C152 on its take-off roll. Fortunately, there was enough look-out and awareness all round to avoid Mr McGoo as he blasted north. Being charitable, the fact that he didn't respond to calls on the CTAF frequency made it clear that he was most likely not receiving, or not listening.
In your case, with 2-way communication established and the aircraft details available, I think a polite follow-up would be appropriate. I'd have also done that but by the time we'd re-arranged the circuit traffic, including accommodating a few new joins, I have to admit that I'd forgotten the call-sign. While there are certainly worse things that can happen, I should have followed it up. If an enquiry meant the pilot in the future at least unmuted his squelch to check for audio volume on start-up (as I and many others do), the follow-up would have been worthwhile.