There are a couple of LLL references concerning relactation for an
adopted baby which may be what is tugging at your memory.  "Nursing Your
Adopted Baby", publication #55, May, 1986, LLLI contains the following:
"...If you are fully breastfeeding a biological baby who is under
twelve-to-eighteen-months-old at the time your adopted baby arrives, it
may be easier for you to breastfeed your adopted baby. Your job is not
to induce a supply in this case, but to drastically increase an existing
one.......A baby over eighteen months may nurse frequently one day and
not at all the next. It will take time to build up a supply sufficient
for a newborn or for tandem nursing. This can be confusing to the
adoptive mother who expects to be able to nurse more easily since she
already has milk...."  This booklet is still available, but I do not
have an updated version.  An even older source is "Relactation: A Guide
to Breastfeeding the Adopted Baby" by Elizabeth Hormann, 1971. It,
however, states that "If you are still nursing a baby, even on a casual
once-a-day basis typical of a toddler, you can reasonably expect
complete success in nursing your adopted child. Supplementary bottles
may be needed occasionally for the first week or so while your milk
supply is building up, but rarely after that." I believe that this
publication has been discontinued.  Don't know if this helps. I can't
imagine how never having nursed at all would be an advantage over having
nursed, at any time.

Sharon K.