Appatently I gifted Ackermans with my hard earned money

So I made a lay bye and didn't pay until eventually it expired. I went to the store to cancel and get my money back, they said because I didn't have the slip they can only make me a voucher and not give me cash. I lost the voucher slip again without having used it and now they tell me they don't have a copy and that it was my loss. So I practically just gave my money to Ackermans???