Outlook.com inbox empty

Yesterday I discovered that my Outlook.com mailbox is empty. Previously it had hundreds if not thousands of messages.

I would expect this in various scenarios:

1) I have activated some sort of rule to archive or delete messages once read.

2) I am accessing the mailbox using a POP3 client which has been configured to delete messages from server once read.

3) I am accessing the mailbox using an IMAP client in which I am emptying my inbox.

Neither of these scenarios applies to me. The only mail client that I use is Windows Live Mail on W7. It defaults to IMAP, and I haven't emptied my inbox within that client.

I am not aware of having made any recent changes to anything mail-related.

Anyone else suffering this, or anyone got any bright ideas?