Hilary Stoupa:When you say you removed & re-added the column - do you mean in the list itself? Or just in the form?
This was via the publishing wizard in InfoPath Designer. First of all, I simply republished the form without making any changes. This didn't do anything so I then used the publishing wizard, removed the column/field, then published the form. After this, I went through the wizard again and added the field (there's screenshots here of what I mean: http://www.mssharepointtips.com/tip.asp?id=1031).
Hilary Stoupa:When you say opening the form in InfoPath filler, do you mean previewing the form? I'm a little confused because you mention its a list form. :-)
Sorry, I mean InfoPath Designer. When I go to the SharePoint list (2013 btw) All Items view, click on the ellipsis of a particular item, the Edit, it opens the form in InfoPath Designer (if you have it installed obviously). I can see all of the missing information on the form.