If you did not verify your actions with the airline before walking away from the flight, then you are classed as a no-show, and unless the terms of your ticket explicitly state otherwise, your entire ticket is cancelled and all monies paid are lost.

You have to notify the airline prior to departure that you no longer intend to travel as planned to have any chance of modifying/refunding your ticket. It does not appear that you did this at the airport, or by phone directly with Etihad, or via whatever agent issued your ticket, prior to walking away. Unfortunately, this is not something you can "work out" after the fact, but one you should have sorted out before walking away (you no longer wanted to travel, so sticking around at the airport, or getting in touch immediately with the airline, should not have been a problem).

Did you have luggage checked in? If you did, and successfully had it offloaded at the place where the delay occurred, then you would have a far stronger case as regards getting a refund/replacement ticket.