You can see what specialists they are using. The bug is just that the little circles don't get filled in. All you have to do is go into the city view and mouse over one of those little circles. You'll either see something like "empty merchant slot" or something like "merchant +2 gold". If you get the former, there's no specialist. If you get the latter, there is. The other way to tell is mouse over the city's gold/science/culture/production output because it will tell you how that total is calculated, including contribution from any specialists.