[Marricio]

pawn Код:

// Somewhere outside a bracket
new PlayerMask[MAX_PLAYERS];

// OnPlayerConnect
PlayerMask[playerid] = random(99999);

stock GetPlayerIDFromMaskID(maskid)
{    
    for(new i, j = GetPlayerPoolSize(); i <= j; i++)
    {
        if(!IsPlayerConnected(i)) continue;
        if(PlayerMask[i] == maskid)
        {
            return i;
        }
    }
    return -1;
}

// /pay
new target = GetPlayerIDFromMaskID(/*id*/);

Not tested. Should work