Re: 156 Undertray?
alleged noise dampening and protection from the elements, I beleive the weather protection line, makes sense but I have not seen issues with cars missing the trays.
and even dealers dont bother repairing them and simply remove trays that are falling off! unless they want more money from you, thus charging for a new one and not simply fixing what you have!
if you can, try to have a look under the car for any damage/wear, highly unlikely but best to check.
*the issue you could have is driving through standing water, the tray could help prevent the engine sucking any water in? maybe?