I had this exact same thing happen to me today in fact. Here is what I did that worked.
Simply delete the field, then replace it with the exact same object. I don't know why it worked or wasn't working in the first place but it fixed the problem and it was easy.
Dear Thom and David;
A little anomaly that I found in certain reports is that if the report is based on a view, make
sure to use column aliases or the T1.column names will cause a glitch in the report
where every time you add or alter a field, it or another will disappear.
This may or may not be relevant in your case, but I thought that I'd throw it out there.
Check it out.
Mike
