Different contributor here. Please permit me to assist.
The solution to the problem is to file a "Debtor's Motion to Quash Garnishment and Compel Satisfaction of Judgment" in the court from which the garnishment was issued, and under the garnishment case number.
Unfortunately, there is no standardized form with which a debtor can just "fill in the blanks" to accomplish this goal. Ordinarily, I would probably tell you that the cost of hiring a lawyer to bring this matter to court would probably be more than the value of the garnishment. However, it could be that by filing the motion and serving the judgment creditor at the last-known address provided to the court would be sufficient notice
such that you could simply appear unopposed in court, testify to the fact that the attempts at service of the motion have been returned unopened, and so the court should release the money, because apparently the creditor has abandoned its case.
Assuming that a lawyer was willing to take a chance you may be able to get someone to take the case on contingency for one third of the amount garnished. So, it would cost you some dough to get the money -- but, 2/3rds of something, is better the 100% of nothing.
For a civil litigation attorney referral, see this link.
Hope this helps.