giffgaff are unlikely to be interested in preventing the dispatch of a sim, as it'll probably cost them more in admin to locate it than it will to simply send a new one to your address (if you choose to order another.)
Sims are free of charge and contain no personal information until activated/used by you, so if you're unable to approach your neighbour for the original, simply order another. If you have not done so already, be sure to order via a members' banner on here as this will get you £5 free credit when you activate (sims ordered from the home page are not eligible for this bonus.)
Your neighbour will probably think that an admin error at giffgaff has printed the wrong door number onto the sim pack. They may even pop it through your door for you when they see your name on it.