While your problem is not exactly the same, I'm pretty sure the way to fix it is to have it added to your cart as instructed in this post
In other words, e-mail firstname.lastname@example.org
and request that they put the DVD in your shopping cart.
Just one more thing.
If I remember correctly, some people have mentioned that when they looked at their shopping cart after Bonnie put the DVD in it, the item was there, but if they left the page then came back, it had disappeared.
So, make sure you proceed with the transaction before you leave the page or you might have to e-mail Support again.