"Prosecution withdrawn" means in a criminal matter that the police do not have a strong enough case and can 't win against the defence in obtaining conviction and ultimately sentence for the accused.
"Prosecution withdrawn" in a civil matter means and, I think the matter was civil here by the tone of your question, that the leasing office of Plaintiff as they were called, withdraws the matter from the Courts for one of three reasons, or more than one reason, as follows:
1. The legal costs to be incurred to gain a judgment as against the
Defendant are more than the Judgment itself would be. In other words, it would cost more to get Judgment than the Judgment itself.
2. The Plaintiff's lawyer or the Plaintiff does not believe that there is sufficient grounds to obtain Judgment in the Courts.
3. The Defendant is debtor proof which means that, even if the Plaintiff were to get judgment, he or she couldn't collect on the Judgment because the debtor or Defendant doesn't have have enough money in the bank if his or her bank account were garnisheed or, they do not have sufficient assets which could be seized to cover the Judgment obtained.
I trust this information will suffice your purposes.
I am a paralegal and have worked for quite a few years in the law.