Someone didn't do their job

I ordered a cake, paid the full price I was told it will be ready on 27/07 I was only given the till slip, I insisted that I be given a manual slip to prove that indeed I did order, the gentleman who was helping me said it was alright and that I should only come with the slip given. Today I went to get my cake and I was told there is no cake and that no order was made for my cake, this really is an inconvenience for me because its for a child's birthday, I was even offered a cake for display - this is an old cake baked who knows when... I am very unhappy with this service.