Retrieve Shopify Vaulted ID from ShopFront API later during checkout

[stevendy]

Hi,
I have a question on how to retrieve a vaulted card Id using shopfront API.
I am using Shopify Payment system without using POS system.

I have an offline selling stand  (machine) with a shopify card reader attached. I develop an app with shopfront api which is deployed in the stand without using a POS app. my use case is like this:
First, the customer tabs the credit card on the shopify card reader and I assume the credit card info is stored on shopify vault on the server (immediately) afterward.
Later (within a few seconds or minutes) the customer selects few products on the stand,  I then create a checkout graphql query in my shopyfront API app and now I would like to link the payment method (ID) to the above vaulted credit card to complete the transaction.
My question is how I could query within shopfront API (or by any other means) to get this vaulted ID (token) to complete the checkout? Do I need to write a separate custom payment app stored on the shopify server to achieve this goal?
Thanks a lot for your help.

Steven