I did not delete my inbox messages, but they were all gone when i logged in

jsut log in to your account then click your inbox and delete all messages that are not very important...you can choose it by ticking the left side of your e-mail and delete it in just 1 click on delete button.

Answered a similar one earlier. You can't. Once their gone their gone forever. Sorry

One_Chance!" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; font-size: 12px; vertical-align: baseline; background-image: initial; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: transparent; color: rgb(0, 0, 0); background-position: initial initial; background-repeat: initial initial; ">You Have Only One Chance!Despite various rumors, there is no way of retrieving deleted messages on Facebook.

Immediately after you delete a message in your private Inbox, you are given the option to "Undo" - above the message - but that is it. Once a message is gone, it's gone; there is no way to recover it later.

Read more: http://www.facebook.com/note.php?note_id=141046243371
the link may be helpful
thanks Roger...

Once you delete messages, they are gone forever :D

update ur phone software from nokia care or nokia pc suite

have you gone into your system settings and changed you option from delete on delivery
if you can change any option that is anywhere close give that a try..

Check your trash folder. If it's there, you still have it. If it's not, then it's gone and you cannot retrieve it. If you deleted the messages they stay in the trash folder for a while, simply save them to your in box again (i have done this a few times myself), if they are not in the trash, they can't be retrieved unfortunately.
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try deleting it from your phone.

Access menu>messages>(Now from this screen you should see your Inbox, Outbox, Drafts, Saved, Etc. Check to see if you are given 'Options').

This should allow you to delete all text messages in each category. If you are not given an 'Options' feature then access your Inbox and from your Inbox use your 'Options' feature to delete all clutter.

Thanks.