Hi Kerry,
Looking at the web site for the Lechuza planters again, I see that the self watering part, what they call the sub-irrigation system, is an "accessory" for the planters. I assumed that this was the only way they come but apparently not. I'm a little confused whether you have the sub-irrigation parts that create the water reservoir or not. If you do have these parts the plug should be there, too, seems to me. Maybe the planter was missing a part?
I do have the sub-irrigation system but I think they have two types of pots some are indoors only
I attached the picture
the other planters have walls that keep water from coming out so you can use the plugs.
here are the pictures of the my pot it did not come with a plug since it is not a pot to use outdoors
as you can see there are no walls or anything from keeping the water in if you had the plug option




I hope this makes sense. I guess the pots I have I can never pot outside if its raining because the plant would drown.