Impeachment of Justice Verma unlikely

According to information retired Justice Yashwant Verma is unlikely to be impeached. In his reply to a notice served by the Speaker , Justice Verma has reportedly stated that he had resigned before the special team began its proceedings and therefore the initiation of impeachment does not arrive against a retired judge. Legal experts also have the same opinion. Now the question is- why was this point not seen before sending him a notice.?.