http://www.britishairways.com/travel/flightops/public/en_gb?p_faqid=5036
if you are travelling in the next day or so- pack in your hand luggage anything essential and it might be an idea to have enough to keep you going for a couple of days. (Please note that normal hand baggage restrictions have not changed) For those who have already lost their luggage, read the link above for what to do next.