If a patient lost an ortho C lenses, another practitioner, even someone experienced in ortho C, would have difficulty replacing the lenses. The lens was determined by the original prescription before the treatment. If the patient had severe myopia, for example, and if she reduced her nearsightedness by ortho C, she cannot go by her reduced prescription to order a new lens. The base curve would be different. The improvement in visual acuity means that the lens is less flat compared to the original lens. You have to go by the original prescription even when the eye became emmetropic. The base curve of that lens is the curve the myopic eye strives to attain. Once the eye achieves that curvature, the patient wears the lens regularly to maintain emmetropia. A different base curve will make the visual acuity worse.
You should give the client the specifications in case you would not be available to order a replacement lens. When ordering online, there is no slot to allow the patient to specify the lens’ thickness. The thickness must be 0.15 mm thick. The “comments” section, or equivalent, is probably the only spot to request that specification. Ordering from an eye care specialist ensures that the thickness is correct.