Hi Nick
When mail messages are deleted from folders other than the Trash folder those messages are moved to the Trash folder. TalkTalk don't delete from any folder other than a scheduled delete from Spam and Trash folders for mail older than 30 days.
As you don't know who deleted those messages you should proceed as though the mailbox password has been compromised. First scan all your email devices to remove potential password grabbing virus, trojan or other malware.
Upgrade the password and in TalkTalk Mail webmail go via the main cog icon menu, All settings menu item and the Security option that you'll see in the left pane. Sign out all devices as a security precaution. Then select Mail in the left pane and scroll down to Rules to delete all (filter) rules that may be spying on your mail messages.
