Axo's should handle pH 8 perfectly well, mine run at 7.5. (a quick google found recomendations of up to 9.0), was it roughly handled at any point, or was the transport time excessive (over 1 day)
I personally would ask for a refund and also recommend the pet store retrains its people, honestly anyone who says an animal looks fine just dead is a bit of a moron. I have had a few recently that have taken a while to get used to prepared food so I would also ask how it was fed and also how skinny it was. and feel its belly to make sure its not got an intestinal blockage due to gravel. gills can be succeptable to ammonia burning if transport was too long, and also look at the tank it came from and the condition of its tank mates.