I just saw this also.  On 0.77.  I had a pioneer plus an archer unit that suddenly got relocated off the left side of the map, so that if I selected them the view was of total unexplored blackness off to the left.  To see if it would clear the problem, I saved the game, and then reloaded it.  On reload, the misplaced units disappeared, but all of my caravans were displayed as described in the OP.  Reloading the saved game again didn't fix it.

In case it helps, here's the saved game.  Note that if you load the game and select the city militia unit that's showing up as the second unit from the top, you're taken to the no man's land like my original pioneer problem.