I don’t see what’s stupid about it. From melon’s links if this guy is impersonating the real pchaos, then the latter needs to be told. If otoh this guy is in fact the same person, he may in fact like the validation of his real identity. It’s no big deal, it’s just a phone call. If the position is that it really is pchaos but he doesn’t wish to confirm that then he can just ignore the voicemail. I see no downside to anyone other than possibly myself in wasting thirty seconds of my time.
Want to know the last Internet stranger related phone call I made? Someone had ordered a dominos and I got ahold of the order. I called them up to ask if they really thought it was sane to be exposing their orders to strangers like me. If I hadn’t been me (or 95% of folk as I still reckon most people are decent) then all sorts of scummy shit could have happened to that dude.
In this case the stakes are far higher (or at least such was my position until BBJ basically showed it was a likely stolen ID but that is hindsight reasoning).
I have also made a phone call to the UK equivalent of 911 on request based on a thread here (and a pm convo leading from that thread) on scanty yet credible info. I don’t really equate that situation with this one other than to say that in my experience it takes someone to be “the guy who does things” and I have adopted a general policy of that being me. A similar situation is on a mini roundabout, which I will analogise my point to the US situation and say there’s four cars who come to a four way stop and all of them wanna turn left. S one has to go first and I try to be that person (except on a roundabout but I translated the analogy in real time 
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This was a relatively substantial post to attempt on an iPad sory for any typos.