pemmican, I am confident that it ('medalled') is made up. Probably just some sports announcer using his unique vernacular. My guess, and it is only a guess, that "to medal" is to win a gold medal.
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pemmican,
I think "gold" might be important here.
If you go the Olympic Medal Standings and drill down on Argentina, you will see that it currently has 4 medals.
Its bronze medal in tennis was won on the 21st. So if yesterday (27th) the Argentina Olympic Team had yet to "medal" then I think the announcer was referring to the gold medal.
Again, just guess