Is there any way to find a sold item?

Expanding on my comment that there is no way to search for an item in the game*.

One answer is to use console commands to add the bow to a known merchant then manually buy back the bow from the merchant. You might want to do this with a merchant who is likely to have acquired the bow naturally though any merchant will do.

First you will need to find out what the FormID of the bow is. To do this you will need to load a previous save where you have the bow. Open the console and run:

ShowInventory

The bow will be listed with it's FormID being enclosed in brackets after the name.

1 - Item Name (FormID) (other stuff)

(I think you can also just drop the bow and left click on it?)

After you know the FormID load up your current save game and find the merchant you want to give the bow to. Open the console and left click the merchant, running:

AddItem FormID

Close the console and buy the item from the merchant as normal.

If you ever encounter the "real" bow then you should remove this from the game by selecting the merchant and running:

RemoveItem FormID

*The toolkit or a custom mod may add this, however they are not released as of this post.