Check the Trash folder on webmail and in particular if there is an arrow beide the Trash folder. If there is an arrow click on it and it should show if there are any folders in the Trash.
If the emails are not there when you check on webmail it means that they have been deleted from the BT servers and they can not be recovered.
The best that BT can do is inform you which device triggered the deletion.
Of no help now but in future you should set up folders to store your emails in rather than treating the Inbox as a storage folder.
