Interesting word. To discover beforehand probably means in regard to an event - to discover it before it occurs. Here is one example of it in context as searched out by
Google -
... "the inability of the government to prediscover such riots as, Lagos (OPC), Kaduna, Shagamu, etc, etc and nip them in the bud."
in
Nzeribe moves to impeach Obasanjo - The Vanguard
The other instances found in Google made little sense to me and were mostly porn sites. Something about prediscovering beautiful babes ...