Lay-bye disappeared!!!!

I have been shopping at the Wonderpark Shopping Centre Woolworths for a while now and have been happy with the service until today. I lay-byed rain boots for kids about 3 weeks ago and today when I went to pay for them in full they were no where to be found. The lady disappeared to the back for over half an hour and nothing. When she eventually came out I went to her to ask her and she told me she can't find them and they are also finished from the floor. I was really puzzled as to why the store allows lay-byes only to have the items disappear. How do I have trust next time that I will be able to get the clothes lay-byed. I am terribly disappointed.