I'm attempting to make my app size smaller by no longer packaging audio files within the app. All is well except for one function. I have FileSavePicker that worked fine when audio files were packaged with the app. Now however, I am unable to get it to work with saving from isolated storage. Ive searched all over and have not seen one example of this. Ive tried posting this at MSDN and even StackOverflow, but not getting any responses. So I thought Id try here. I figure someone out there has to know if this can be done and what I would need to change.

As it stands now, I receive the following Exception: System.IO.FileNotFoundException at this line in my SoundData model:

StorageFile file = await folder.GetFileAsync(SavePath);


SoundData:

Code:
private async void ExecuteSaveSoundAs(string soundPath)
        {
            
            StorageFolder folder = Windows.ApplicationModel.Package.Current.InstalledLocation;
            StorageFile file = await folder.GetFileAsync(SavePath);

            FileSavePicker savePicker = new FileSavePicker();
            savePicker.SuggestedSaveFile = file;
            savePicker.FileTypeChoices.Add("MP3", new List<string>() { ".mp3" });
            savePicker.ContinuationData.Add("SourceSound", SavePath);
            savePicker.SuggestedFileName = this.Title;
            savePicker.PickSaveFileAndContinue();
        }
   
        public SoundData()
        {
            SaveSoundAs = new RelayCommand<string>(ExecuteSaveSoundAs);            
        }
App.xaml.cs:

Code:
private async void Application_ContractActivated(object sender, Windows.ApplicationModel.Activation.IActivatedEventArgs e)
        {
            var args = e as FileSavePickerContinuationEventArgs;
            if (args != null)
            {
                StorageFile file = args.File;
                if (file != null)
                {
                    // Prevent updates to the remote version of the file until we finish making changes and call CompleteUpdatesAsync. 
                    CachedFileManager.DeferUpdates(file);
                    // write to file 
                    var sourceFilePath = args.ContinuationData["SourceSound"].ToString();  
                    StorageFolder folder = Windows.ApplicationModel.Package.Current.InstalledLocation;
                    StorageFile sourceFile = await folder.GetFileAsync(sourceFilePath);

                    IRandomAccessStreamWithContentType sourceStream = await sourceFile.OpenReadAsync();

                 var bytes = new byte[sourceStream.Size];

                 var sourceBuffer = await sourceStream.ReadAsync(bytes.AsBuffer(), (uint)sourceStream.Size, Windows.Storage.Streams.InputStreamOptions.None);

                    await FileIO.WriteBufferAsync(file, sourceBuffer);
                    // Let Windows know that we're finished changing the file so the other app can update the remote version of the file. 
                    // Completing updates may require Windows to ask for user input. 
                    FileUpdateStatus status = await CachedFileManager.CompleteUpdatesAsync(file);
                }
            }
        }
SoundModel:

Code:
private SoundGroup CreateSoftwareGroup()
        {
            SoundGroup data = new SoundGroup();

            data.Title = "OS/Software";

            data.Items.Add(new SoundData
            {
                Title = "Test1",
                FilePath = "https://xxxxx.test1.mp3",
                Groups = "Test",
                SavePath = "Test1.mp3"
            });

            data.Items.Add(new SoundData
            {
                Title = "Test2",
                FilePath = "https://xxxxx.Test2.mp3",
                Groups = "Test",
                SavePath = "Test2.mp3"
            });