I want to take some event data from AudienceStream I have and join the event's active device from the visit associated with that event, as the event data only contains the unparsed user-agent.  However, I cannot seem to find the "visit - id" on the event data at all.  There is a Tealium session ID, but that field seems to have nothing to do with visits, or at least I can't find a field with session ID values in it on visit data.

It seems like the logical thing to exist.  Visitor ID is on Events and Visits and Visitors data, why wouldn't any events that make up a visit be associated by a Visit - ID?  What am I missing?