Blizzard did not have a human GM at your exact place at that exact time. That isn’t surprising - there are about 800,000 players. Blizzard does not have 800,000 GMs.
Blizzard bans thousands of bots each month. But many of them come back on different accounts, which aren’t yet banned. They even farm the same places. Blizzard cannot eliminate all botting.
What does it take to get YOUR SPECIFIC bot banned? A custom game, where you pay $700 per month to have instant human service. You can’t get that for $15 per month. You can’t get personalized service for you, at that price.
All you get is “my reported bot goes into the pool of thousands of other bot reports”. Each one has to be reviewed by a GM. Eventually they might find your bot, when it is actually botting, verify that you are right and ban it.
But first they will make sure it isn’t a player or multiboxer that just seems like they are botting. A lot of bot reports are incorrect.