The given sentence is more like "I do not see any reporters" (you were expecting reporters but couldn't find any) "Én nem látok egy riportert" is "I do not see a reporter" (not often used, but similar to last one) "Én nem látom a riportert" is "I do not see the reporter" (a specific reporter you were looking for)
Very good point, that was my translation too and luckily it's accepted. "Nem látok egy riportert" sounds like you can't see a certain, "unnamed" reporter; "egy riportert sem" would sound like "no reporters at all", hence I think it's much more closer to the sentence presented here
It's not a good idea to treat translation as word-for-word mapping. "I do not see reporter" sounds just wrong in English and "Én nem látok egy riportert" sounds like there is a certain (but unnamed) reporter that you don't see. Also, in English it may be more common to use "I can't see" that you definitely don't want to translate as "Nem tudok látni" because that wouldn't fit in Hungarian.