Three materialists chance upon a resurrection....
Ok first lets put aside the rather strange notion that people would describe themselves as 'materialists'.
On to the meat.
First you're phraseology of itself is biased and conveys a presumption. They wouldn't 'chance upon a resurrection', they would chance upon a person where there is a claim that this individual had been dead and was now alive again.
In which case I (if it were me) would want to investigate that claim. Firstly I would want to ascertain beyond doubt that the person alive now is the same person who it is claimed had died. And that evidence would need to be independent and objective - e.g. DNA/ dental records etc.
Secondly I would require clinical evidence that the person had actually died - not just in a deep coma, near death, or in a state where resuscitation was possible. And for the claim to be sustained to be convinced beyond doubt that the person had been in that state of clinical death for a significant period of time - not just seconds, but - hey three days or longer. Again the evidence would need to be independent and objective.
Finally I'd need to confirm that the person now alive is real - not some clever illusion, hologram etc and genuinely living (that I wasn't suffering some strange hallucination) - so several, independent and objective witnesses that can be independently questioned about their interaction with this once dead, now alive person. I'd expect the claim of living to be sustained over a period of time - not a one off chance encounter that could be subject to misunderstanding/misinterpretation/mass hallucination/group think, but verified repeatedly and independently over a period of time.
Were it to be the case that all these criteria were met my interests would turn to the cause of this phenomenon. And I would want to look for anything unusual about the genetic/epigenomic/phenotypic make up of this person that might help us explain the phenomenon. Or perhaps that the person had been subject to successful cryogenic preservation etc. It might be that current science wouldn't provide an explanation at this time, in which case I would conclude that we have a currently unexplained phenomenon.
What I wouldn't do is firstly simply accept that if someone says the person was dead and is now alive that that means it is true.
Also what I wouldn't do is do a 'god of the gaps' and conclude that because we don't understand the phenomenon that it must be 'cos of god'.