[Ysharros]

Relogging might solve the issue for you, by either showing the assembly recipe you need (which should be in the window you mention when you target an assembly bench), or by simply dropping the upgraded tool on you when you log back in. This assembly thing has had problems for a while, and I believe the "whoops here you go!" loging to upgraded tools is a way round it.

If neither of those happens, I'm not sure how to fix it. That said, the higher class crafting vendors (the ones with the level 20 gear for sale) also sell all +2 tools at very little cost, so all is not lost. I can't tell you where that vendor may be in Halgarad but I'm reasonably certain there will be one somewhere in town.