In what way does the author of Hebrews argue that every transgression or disobedience received a just retribution? Therefore we must pay much closer attention to what we have heard,
  lest we drift away from it. For since the message declared by angels
  proved to be reliable, and every transgression or disobedience
  received a just retribution, how shall we escape if we neglect such a
  great salvation? It was declared at first by the Lord, and it was
  attested to us by those who heard, while God also bore witness by
  signs and wonders and various miracles and by gifts of the Holy Spirit
  distributed according to his will. (Hebrews 2:1-4 ESV)


The author appears to be arguing in the past tense, as if to say that every transgression or disobedience has already received a just retribution, but considering the fact that the day of judgment has not yet taken place, it doesn't seem like that is possible.

What does the author of Hebrews mean?
The note in NAB explains this:


  The author now makes a transition into exhortation, using an a fortiori argument (as at Heb 7:21–22; 9:13–14; 10:28–29; 12:25). The word announced through angels (Heb 2:2), the Mosaic law, is contrasted with the more powerful word that Christians have received (Heb 2:3–4). Christ’s supremacy strengthens Christians against being carried away from their faith.


There is also a reference to Acts 7:38, 53; Gal 3:19.


  Acts 7:38 It was he who, in the assembly in the desert, was with the angel who spoke to him on Mount Sinai and with our ancestors, and he received living utterances to hand on to us.
  39 “Our ancestors were unwilling to obey him; instead, they pushed him aside and in their hearts turned back to Egypt,
  40 saying to Aaron, ‘Make us gods who will be our leaders. As for that Moses who led us out of the land of Egypt, we do not know what has happened to him.’
  41 So they made a calf in those days, offered sacrifice to the idol, and reveled in the works of their hands. ...


The letter to the Hebrews is directed to an audience familiar with the Old Testament. The author is calling to mind all the past retributions for transgressions against the Mosaic law. "If then it was so, when God announced it through angels, will it not be all the more so now, since it has been announced through Christ Himself?"