The checks for amended returns go to the address listed on your amended return form 1040X. Isn't it your address on your return? Did you move? You need to have the IRS put a trace on it.
Was it for an actual amended 1040X return you mailed in? Or did you just fix your original return and efile it? If it was for an efiled return were you having the fees deducted from it?
What makes you think that it is a TurboTax bank account, did you search the routing number to a particular financial institution? TurboTax doesn't have its own bank like you say above ("in your bank"). And most of us answering questions have no affiliation with TurboTax, just sharing our personal expertise. You need to contact the IRS if you think your refund went somewhere it shouldn't have - they can track it and tell you where it went.
The IRS would not be able to send your refund to TurboTax. In fact, if you sent in a paper mailed, amended 2016 tax filing, you would have had a paper check mailed to the address on your return and W-2.