Q: When I go into a folder in mail every thing in it deletes and is lost!

Are these items possibly past the date that you syncing?

(Settings > Mail, Contacts, Calendars > Mail Days to Sync)

Hmm... this option doesn't seem to be in iOS 7.  Right?

It is not an iOS 7 setting, it's a mail account setting. My Exchange account has that, but not some of the other POP and IMAP accounts. The mail should come back, I should think, as long as you haven't gone in and deleted them and they are within the date range. Give it some time to sync. If it's still not back, do the reset: hold down the home button along with the sleep/wake button until you see the apple, then let go.

If the email was on a computer, use one of its backups to retrieve the lost emails.  On the iOS device, you can't get back deleted (I assume "lost" means deleted) emails since they are not included in a backup.  If the email service is a POP service, then the server may still have it.  If IMAP, then when you delete an email on a device, it is deleted from the server and all other devices connected to that email account.

Great!

more info on changing a sync date, what are the steps and what date was selected, my mail is gone as well

thanks