To isolate all the calls which were not filtered by an IVR (matched Caller ID numbers) and therefore routed to a more specific, useful group of people, you should go to Reports, Then select drop-downs as follows:
Call Reports / Historical Voice Calls V2 / Date Range / Run Reports
Then select Traffic Analysis to show all the calls within that date range.
On the left hand side you see a visual representation of all the inbound numbers and how they translated to the terminating destinations. If you find the default hunt group and click on it, you'll only see the numbers which went there (and therefore not picked up by an IVR).