It sounds like the simplest way to do this would be to contact the original creator of the object to assist you. That person will have the UUID of the texture you're looking for, which you can then use in your project.
On the other hand, if you created this piece, you will also own the textures in your inventory. I've made things too and can't remember which textures I used, so here's what I do (minus the UUID parts...) Just rez the object, right-click to edit it, click the Texture tab in the Edit window, choose the select texture option and then click on the object, in the individual area which has the texture you're looking for. Then, click the texture box (the left one) in the edit window. A second window will open up, where you will be able to see the name of the texture used. You MAY be able to right-click the name of the texture file and copy the UUID but if not, simply close all the open windows, and then go to your inventory to search for the name of the texture file used. You can easily right-click its name and copy the UUID.
Good luck with this!!