Credit Card Fraud

My brother lives in Seoul. He booked a holiday to Vietnam about 2 months ago using my mums cc
However someone else also used the card to book flights to china.

I contacted the travel agency that was used to book the Chinese flights and they provided the names of the two people who booked the flights.
(by the time the cc compnay sent out my mums monthly statement the flights had already been used)

So i have provided the credit card company all the correspondence(email)between myself and the travel website.

The credit company actually send another bill asking for the money and interest on it also. My mum had to phone them to tell them she had sent back their declaration form telling them to proceed with the investigation.

However the cc company said they didn't recieve the form even though my mum sent it by recorded delivery. They then rang back saying they did get it afterall :rolleyes:. If they cant even find forms then i dont hold out much hope for their investigation

The cc company have stated an investigation will take 45 days. What happens after this? Will they only clear my mum if they find the culprits?

Thanks for any help