When storing built items in workshop, what happens to them?

I wanted to move one of the medium power generators I built to a different location in my settlement. So I thought I could store it in my workshop, run over to the new location and place it from storage.

However selecting "Store in workshop" just removed the item, it doesn't appear in the workshop item list, I didn't get any extra resources (so it wasn't scrapped) and I can't see any section from the workshop menu to access stored items.

Is my power generator just gone now? Or can I access it from somewhere so it can be placed again?

They're stored in the same place you build them from. If you store a generator, there will be a 1 on the generator in the build menu, and when you go to place one, you won't need to pay the resource cost.