Emails not showing up after a particular date Exchange 2007

I am using Exchange 2007 and for one particular user his inbox is not showing emails after 14th Feb 2013 both in the outlook and OWA suing the IMAP.The total items in his mailbox including inbox, deleted items, sent items etc comes to 461 while the item count on the sever is 622.

There is abundant space in the mailbox, more than half empty.

I have a feeling that he might have configured a POP3 account around that time on his IPad, which could have led to the deletion of the files.But he is not ready to admit that and wants his emails back.Is there any way on the server side to check if he did something like that.Or is there any way to recover those files.