This does raise the question of how knowledge of Vulcan's fate propagated in the Federation. While the process was ongoing, Nero's jamming would prevent the news from getting out. The Enterprise
in turn might still be unable to communicate due to the damage suffered (and for that reason couldn't tell Delta Vega about the castaway, either). Would the supposed Vulcan escapees be able to contact the media?
If there was no immediate coverage of the event, we might still consider Scotty reasonably alert and deduce that the skies above Delta Vega did not feature any calamities of note. If there was coverage, then Scotty is far from alert and might have missed Armageddon next door.