@Chris I don't think there will be a reference to the deleted row, the suitelet is a form and once submitted the form will go to the server with the data present in that form. You can make the Sublist no editable and create a checkbox per line to indicate when the user wants to remove a row, then you get all the data servers side and handle the logic to the deletion of that row.

No delete reference... I was afraid of that. This is a bummer.

@Chris Or you can handle the rows deletion with a Client Script and store the deleted row in a hidden field.