Yes it could have been a GM. Another way to check if they are legit other then the usual coloured (blue?) text is checking their corp.
CCP employees are in their own co
orp called CCP, which is not accessible by normal players.
If it were to be a normal player, they likely will get a banhammer soon as pretending to be a GM is against game rules.
But yeah, it is known that CCP employees sometimes visit new player systems to help and chat the new players.