Getting Strings from PlayerFiles

So I have a plugin, that creates a File for every player, that joins. Its Named "PLAYERUUID.yml"
Now I want to make a /seen command. My problem is, that my method only works on online players, and i have no clue, how to change that! Could you help me?

 

@OverDodo
Can you post the section of code that is supposed to perform the function that you're having trouble with?

 

Bukkit#getOfflinePlayer?

 

I don't know if getOfflinePlayer is a thing, but you could also load your players from the files to an array or something, and scan that array for the username that the commandSender specifies in the first argument. Although this may not be the most efficient way to do it, because of ram usage and especially for when the server reloads/restarts.