Note also that if you didn't make Argentina an active league, and you're playing with a Small DB, then the odds are there are no
real players in Argentina .. or few enough that they honestly didn't find them.
Also, if you set a specific search criteria, you can shoot yourself in the foot if you make it too narrow.
Taking the Argentina inactive / European club / Small DB example: if you tell the scout "Left backs under the age of 18", he will come back with nothing because there are no left backs under the age of 18 in Argentina on your save game. Newgens in an inactive Argentina often come into existance at age 19, 20, or 21, when they are considered to have risen into such promise that somebody outside of Argentina might be interested in them.
In general, scout your active leagues, unless you have a Large DB .. in which case, go anywhere you want .. but be gentle on the search parameters.
. . .
The other thing that occurs to me is, are you ignoring the "Scout Knowledge" and "Club Knowledge" indicators?
If you are sending a scout with no knowledge of the country, who doesn't speak the language, to a nation your club has no knowledge of ... well, he's pretty much s.o.l., isn't he?

Send scouts to places they know .. or build their knowledge by sending them to places the club has some knowledge of thanks to a Coach, a Feeder Club, or the Manager.