Unfortunately, attempted threats in the District of Columbia would not qualify you for a jury trial because the offense carries 180 days and/or $1000.00 dollar fine. Threats would have qualified you for a jury trial because it carries 6 months in jail. The government routinely amends the threats charge to attempted threats so that you will not be eligible for a jury trial. Lastly, your time for noting an appeal on this issue has expired.
This answer does not establish an attorney client relationship.
You couldnt get a jury trial because the attempted theft charge didnt carry a maximum jail sentence of six months or more. If you didnt already file a notice of appeal, you are likely unable to do so now. One possible exception is if you asked your lawyer to file a notice of appeal and s/he said s/he would but didnt and you relied on the attorney to follow your wishes. Another possible route you could take to challenge the conviction is a motion for a new trial based on newly discovered evidence, but you would have to be able to argue that you couldnt have discovered this evidence before now.