The presence/absence of the `bolus` field seems like a good indication to me.

Fwiw, though, I believe the problem you are pointing out has nothing to do with how wizard events are stored, but rather with how we are choosing to display carbohydrate consumption.  We should rethink how carbs should be displayed given that the only data we have is stuff from the interaction with a bolus wizard.  Once we actually do have food events, we will definitely need to indicate which is which when visualizing.