Once a fighter is retired to the Bahamas (and cannot be un-retired), you can reveal his hiddens for a fee of 5 VIP days. It can be any fighter, not just your own.
Fighters You've Revealed
Fighter
Average
Hidden
Highest
Rank
Last 50 Revealed by Others
Fighter
Average
Hidden
Highest
Rank
Your Old Fighters
Fighter
Record
Highest
Rank
*note - earlier in the game, hiddens were not saved when a fighter was retired, so only more recently retired fighters will show up.