vector getting empty in draw method problem

Artefact.cpp

#include "Artefact.h"

Artefact::Artefact(string cascadepath_, string name_, string description_, ofImage mockup_){
    cascadepath = cascadepath_;
    name = name_;
    description = description_;
    mockup = mockup_;
}

Artefact::Artefact(){
}

Artefact::Artefact(ofDirectory dir){
    // create an artefact object from a directory, including a config file
    string configjson = ofFilePath::join(dir.path(), "config.json");
    
    ofxJSONElement result = ofxJSONElement();
    
    // Now parse the JSON
	bool parsingSuccessful = result.open(configjson);
	
    if (parsingSuccessful) {
		cout << "parsing of " << configjson << "succesful" << endl;
        cascadepath = ofFilePath::join(dir.path(), result["cascade"].asString());
        name = result["name"].asString();
        description = result["description"].asString();
        mockup.loadImage(result["mockup"].asString());
    } else {
        cout << "could not open " << configjson << "\n using empty values. please check your artefacts folder for proper functionality!" << endl;
        cascadepath = "";
        name = "without name";
        description = "without description";
    }
}

Artefact.h

//
//  Artefact.h
//  PhysicalFinder
//
//  Created by tom on 11.07.14.
//
//

#ifndef __PhysicalFinder__Artefact__
#define __PhysicalFinder__Artefact__
#include "ofMain.h"
#include "ofxCv.h"
#include "ofxJSONElement.h"



class Artefact{
public:
    
    Artefact(string cascadepath_, string name_, string description_, ofImage mockup_);
    Artefact(ofDirectory dir);
    Artefact();
    
    std::vector<ofRectangle> foundObjects;
    string cascadepath;
    string name;
    string description;
    ofImage mockup;
    
private:
    
    
};

#endif /* defined(__PhysicalFinder__Artefact__) */

ofApp.cpp

#include "ofApp.h"

using namespace ofxCv;
using namespace cv;

void ofApp::setup() {
	ofSetVerticalSync(true);
	ofSetFrameRate(120);
	finder.setPreset(ObjectFinder::Fast);
	finder.getTracker().setSmoothingRate(.3);
	cam.initGrabber(1280, 960);
	ofEnableAlphaBlending();
    
    
    /* stepping through config/artefact directoy
     and creating objects for each artefact */
    
    string path = "artefacts/";
    ofDirectory dir(path);
    dir.listDir();
    
    for(int i = 0; i < dir.numFiles(); i++){
        ofDirectory curDir(dir.getPath(i));
        if(curDir.isDirectory()){
            // curDir is a single artefact dir
            // with the config.json, 3d file, cascade file inside.

            Artefact curArtefact = Artefact(curDir);
            artefacts.push_back(curArtefact);
        }
    }
}

void ofApp::update() {
    
	cam.update();
	if(cam.isFrameNew()) {
        
        for(Artefact a : artefacts){

            finder.setup(a.cascadepath);
            finder.update(cam);
            for(int i = 0; i < finder.size(); i++){

                ofRectangle r;
                cout << "found objects: " << finder.size() << " in " << a.name << endl;
                r = ofRectangle(finder.getObjectSmoothed(i));
                cout << " size of foundobjects before: " << a.foundObjects.size() << endl;
                a.foundObjects.push_back(r);
                cout << " size of foundobjects after: " << a.foundObjects.size() << endl;
            }
        }
	}
}

void ofApp::draw() {
    ofSetColor(255);
	cam.draw(0, 0);
	for(Artefact a : artefacts){
        for(int i = 0; i < a.foundObjects.size(); i++) {
            // wird GARNICHT AUSGEFÜHRT!!
            cout << "draw2" << endl;
            cout << a.foundObjects.size() << endl;
            ofRectangle object = a.foundObjects[i];
            ofNoFill();
            ofSetColor(0, 30, 200);
            ofRect(object.getPosition(), object.width, object.height);
        }
    }
}