I'm not sure that it cost you silver. In the past when this has happened to others BAEC sometimes has usually been able to sort it out once the points post in the new year and are then deducted and credited back to the old year. If by some chance things don't get sorted just give them a call again or send Nicci a PM with the details.
See:
http://www.flyertalk.com/forum/briti...-credit-2.html
http://www.flyertalk.com/forum/briti...ing-avios.html
http://www.flyertalk.com/forum/briti...ting-date.html