This one does seem to be a bug, usually if no parts are available there is a circle with a cross through it on the screen, in this case it shows the parts available allows you to purchase them, but then doesn't install. This happened to me the other day.
The F430 was shocked at your choice of parts, it was horrified, so while you weren't looking it took them off. Joking but theres been several references to this, its a bug most likely.