If you have a Damier Ébène Neverfull, there is no "vachetta" on it. Only dark brown treated leather. You can always take your bag to Louis Vuitton and they will provide you with an estimate to repair your bag. In most cases, they won't ask for a receipt and even if they do, simply say the bag was a gift.
Be aware that if your bag is repaired by a third party, Louis Vuitton will refuse all other repairs down the road.
What people refer to as "vachetta" is untreated cowhide leather (very pale, darkens over time). This leather is mostly found on Monogram canvas, Damier Azur, and Monogram multicolor pieces.