Get Lync Conversation Text

Hi there, I'm coding a CWE, and I need to get the conversation text. For now, I'm saving all the instant messages sent and received, from the instant message modality, and save it in a string list.

private void MainViewModel_InstantMessageReceived(object sender, MessageSentEventArgs e)
        {
            try
            {
                _textList.Add(new ConversationText(DateTime.Now.ToShortTimeString(), ((InstantMessageModality)sender).Participant.Contact.GetContactInformation(ContactInformationType.DisplayName).ToString(), e.Text));
            }
            catch (Exception err) { MessageBox.Show(err.ToString()); }
        }

The thing is, when I get a new message and I have my conversation window closed, I miss the first sent text(I don't have my app running yet). Or if I close my app and reopen it.

Is there anyway to accomplish this??

Hope you can understand me, English is not my native language