I think you can't use your own id, you have to use the id of the Google Form's "Item" object. You can figure out the id by viewing a prefilled form. In the Form edit screen, click "Responses", "Get Pre-filled URL". Fill in the field that you want to use and click Submit. On the new page, you are given a URL in "Share this link to pre-fill the responses" . Examine that url and you can see "get" arguments like ?entry.265525444=mytext . Replace mytext with whatever you want to be in the field.
This will display the field on your form, however. I myself was searching for how to make such a field readonly or invisible when I got here, but I hope this shows you a new direction to try.