Lost emails in Exchange

I have a customer that has exchange running on their server, the hard drive is filled to capacity. They keep all their emails. So I setup archieving on their local computer, so I can free up space on their server. But during the process the messages dispeared. The server got more space and the archieve file is only 265kb in size. Now the customer needs something from a year ago, and can’t find it. Any help, where did the messages go.