I am citizen from Kosovo who visited London few months ago (march 2013) and the day I left the UK from Luton airport I claimed my VAT refund on some shopping I have done in London. I asked at the information desk for directions, who advised me to put all my bills in one envelope and put it in VAT BOX. I handed my receipts to Luton's VAT box with a cover note with address and bank details, but unfortunately although seven months passed there is no refund on my credit card.
There is a specific process that you must follow to obtain a VAT refund - from obtaining the correct paperwork from the retailer where you purchased the goods, to showing the goods to customs staff at the airport at your point of exit from the UK/EU.
Based on your description, I suspect that you did not follow the correct process. Without doing so, you will unfortunately not be receiving a refund, and there is nothing you will be able to do in order to obtain one.
You can find the UK process on HMRC website. The process for other EU countries is similar, but there are slight differences based on where the purchases were made, and which country you leave the EU through.