you should be able to achieve the same result by
promoting (aka publishing) the field in question. That's what you do to get
SharePoint to recognize the data and store it in a list field.
FYI, one way to avoid this kind of confusion would be to create content type
and then base your InfoPath form on that. Then when you need a new field,
you just create it in the content type and pull it through on the form. The
alternative would be to publish your form *as* a content type, but that
seems to require admin privileges, etc. that may or may not be within your
reach on a particular server.
Of course you can just do the field promotion thing and carry on... it's
been a while since I was the "InfoPath expert" (read: the guy who got stuck
doing IP most often) at my old employer, so I may not have the most
realistic perspective.