I have heard that FOP won't retrieve anything not found on the given page, but I've not used the tool and cannot confirm this for you.

It depends on the release and some context. The most recent
release can retrieve markers from previous pages. There are
still various problems with the page scope though.

BTW the spec seems to be ambiguous on which marker is to be
retrieved if several eligible markers are found on, say, the
previous page (and non on the current). FOP picks the last,
but I didn't find anything in the spec to back this strategy.