TurboTax does not use 8879 or provide a filing letter. Form 8879 if used by paid preparers. You are doing your own taxes with TurboTax and do not use 8879.
Let the financial institution know that you cannot provide those proofs of filing. Explain that you filed yourself with TurboTax and do not have them. Ask for some alternate form of proof of filing. There is an e-file number generated when you file and the helpdesk may be able to provide that number to you.
I am not sure if that is information that they can share with the taxpayer. I would suggest you call the helpdesk and ask if there is any proof of filing that they can provide to you.
