Several email folders where entire contents have been deleted

I have just discovered the contents of several email folders have been deleted, there is only one email in my sent box from last night, previously containing about 100 pages of emails, and just a quick check I see that several other folders are also empty.
These emails are irreplaceable!
NO, I have not accidentally deleted them all, it is a fault with Talktalk and I have only access them from webmail on my PC.
Please can someone help with getting these returned, thank you.