ActionScript 3: Error #2025

My code works fine. It's suppose to bring in one image when the user presses 1 and swap it out for another when he / she presses 2. But, when I presses 1 or 2 after having previously pressing either the same number I get a #2025 error. Ex: Pressing 1 then pressing 1 again.

ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller. at flash.display::DisplayObjectContainer/removeChild() at warren_fla::MainTimeline/reportKeyDown2()

Code

import flash.events.KeyboardEvent;

var bdata = new image1(stage.stageWidth, stage.stageHeight);
var bdata2 = new image2(stage.stageWidth, stage.stageHeight);
var bmp = new Bitmap(bdata);
var bmp2 = new Bitmap(bdata2);

function reportKeyDown(event:KeyboardEvent):void 
{ 
if (event.keyCode == 49) {
    //trace("1 is pressed");
    bmp.x = 230;
    bmp.y = 150;
    addChild(bmp);
}
if (contains(bmp2)) {
    removeChild(bmp2);
    }
}

function reportKeyDown2(event:KeyboardEvent):void 
{ 
if (event.keyCode == 50) {
    //trace("2 is pressed");
    bmp2.x = 230;
    bmp2.y = 150;
    addChild(bmp2);
    removeChild(bmp);
}

} 

stage.addEventListener(KeyboardEvent.KEY_DOWN, reportKeyDown);
stage.addEventListener(KeyboardEvent.KEY_DOWN, reportKeyDown2);

You are removing bmp without checking if it is already a child.

function reportKeyDown2(event:KeyboardEvent):void 
{ 
    if (event.keyCode == 50) {
        //trace("2 is pressed");
        bmp2.x = 230;
        bmp2.y = 150;
        addChild(bmp2);
        if(contains(bmp)) 
            removeChild(bmp);
    }
} 

Also your code can be refactored into this simpler version :

import flash.events.KeyboardEvent;
import flash.ui.Keyboard;

var bdata = new image1(stage.stageWidth, stage.stageHeight);
var bdata2 = new image2(stage.stageWidth, stage.stageHeight);
var bmp = new Bitmap(bdata);
var bmp2 = new Bitmap(bdata2);

function reportKeyDown(event:KeyboardEvent):void 
{ 
    if (event.keyCode == Keyboard.NUMBER_1) {
        swapBitmaps(bmp, bmp2);            
    } else if (event.keyCode == Keyboard.NUMBER_2) {
        swapBitmaps(bmp2, bmp);            
    }
}

function swapBitmaps(first:Bitmap, second:Bitmap):void
{
      first.x = 230;
      first.y = 150;
      addChild(first);
      if(contains(second)) {        
           removeChild(second);
      }
}

stage.addEventListener(KeyboardEvent.KEY_DOWN, reportKeyDown);