'01 Caravan Radiator Drain Cock Position

I recently had to replace the radiator in my '01 Caravan, which I did myself no big deal, but a month later out on an errand I noticed a large puddle of coolant under the veh, and barely made it home amid a cloud of coolant smoke. Upon investigation I found that the drain cock was gone. I was able to get a new rad under warranty and have installed it. My question is what exactly is the proper closed position for the drain cock. Should the tab be verticle or horizontal. I didn't pay too much attention to the first rad I installed but the second one I noticed the drain cock tab was verticle when I rec'd it. My brain says it should be horizontal to be closed. Because of what happened with the 1st rad I'm now paranoid to drive anywhere. Please help.

Thanks