I think I have a solution. Things are saved by there position correct?
So when you log back the items are still there but they are just detached.
So what about creating an I'd to each new item. Like the current Id for this item is 1. If you buy a new item that new item's Id will become 2. This makes each item unique.
The ids will work as a group connection Id. Like 1:2:3
1 is the blade. 2 is the guard. And 3 is the handle. The semicolon acts as that attachment between two ids.
Basically when the game saves the ids. If you load back in the game. The gamewill automatically attach those ids based on your save file. Fixing the issue that your having.