Sticky situation

I think I've mentioned on here before that I work for the same company as my dad. He works in the head office and I'm a relief cashier. Over the past couple of weeks a well-known gang has been trying to have us over in a few of our shops. I only work during holidays so I'm not as clued up as to who's who when it comes to con-artists.

I fully admit that I made a mistake and forgot one of the first rules of my training and by doing this, ending up costing the company about £600 via this gang. The matter has obviously gone round head office and they are trying to establish how many of us fell for the same trick etc. However, my dad has decided to tell me some information which I'm not sure I ought to know. He says it's been decided that I am blameless and they are going to take disciplinary action against the manager I worked with who let me make the mistake. I feel really bad about this and I don't her to lose her job because I made a mistake, even though she should have stopped me.

Anyone been in a similar situation?