When in the workshop menu, if you use O button to, "store item in workshop" where the hell does it go?

It is not in the workshop or player inventory.

If you select to build the same item again, you must do so with new materials.

This is rediculous.

They are only stored in the same location that they were removed from, i.e. you can't remove the power armor station from red rocket and use it in the castle. If you have an item stored you'll see a number next to the name when you are in the creation menu. It will say Power Armor stand (3) to indicate how many you have stored. Building the next 3 will be free of mat costs and you'll see the number go down when you do build. So it's not bugged, just not explained well.

Hope this helps.

This is wrong. The numbers in the brackets indicate how many of that item you can build using your current inventory. The items which you store using O are missing.

You'll notice when you have one stored and build the item the components (ceramic, glass, etc) will not go down.

The number of stored building components will actually show below the little graphic for the item in the list. They don't store in any physically accessible container. And yes the number in parentheses next to it is what you can build using current available materials which is a separate number.

http://i63.tinypic.com/35c2881.jpg