Tell us how you were using TalkTalk Mail i.e. webmail or an IMAP email account or POP3 email account on a device. And exactly what you did.
If you were using TalkTalk Mail webmail and deleted a folder from the folder actions menu then you would always receive a warning pop-up to ask if you really wanted to delete that folder. If you confirm deletion then that folder and any sub folders it contained would be in the Trash folder for 30 days before system deletion. Sub-folders are indicated by an inward facing arrowhead so select that arrowhead to expand and show sub-folders. If you deleted a folder from the Trash folder after confirming deletion then that's gone and there is no TalkTalk backup available.
If you inadvertently moved the folder then the last move action would still be present in the move menu. Look for the inward facing arrowhead on existing folders to see if that reveals the moved folder and its sub-folders.
If you deleted a folder using an IMAP email account then sign in to webmail to look in the Trash folder. But that synchronisation of Trash folders depends on what action you have set up in your IMAP email software. The deletion may move the folder to a local folder on the device.
If you deleted a folder using a POP3 email account then that folder would always be on the device and follow the actions set up for mail deletion.
