If an "ignore" section is added to the system, or a code prefix meant to make the system do the same thing then this kind of thing can be stopped.

I used to use sage line 50 for a retail outlet, and because of records laws I still had to keep information regarding items I had discontinued (non-profit/ manufacturer end of line etc) on the system. A simple prefix allowed it to ignore all of them when calling up codes for sales, re-ordering and stocktake. I don't know why all systems don't do it.

I go regularly to a hardware outlet, and it's pretty common to be sold an item under the wrong code (and therefore price) say 16mm ply WBP instead of normal. Obviously I only point out the mistake it it's over the normal price, if it's under it's their own fault for not sorting it despite numerous errors, and no I don't feel bad because it's a multi million pound company that could afford to fix it.