Hi MGibson and welcome to our forum,
There is a column in SharePoint that keeps the ID. The problem is that you have to wait until the form is submitted to make sure that you are indeed 2 and not 3 (in case someone else submits before you do). I recommend submitting the form on open and then querying the SharePoint list to get the ID and autopopulate the field. That should work.
Patrick Halstead
Project Manager at Qdabra