A true "judgment proof" debtor is one who is unemployed with no future prospects of finding employment, one who lives on government benefits, pensions, or retirement, and has no funds in his or her checking or savings accounts that do not stem directly from those exempt funds. What you have been told is correct in that a judgment against them can't be collected, because there is nothing to collect.
But one tool to determine if a creditor is truly judgment proof is the judgment debtor
examination under Rhode Island General Laws 9-28-4, which subjects the creditor to questions about his or her circumstances, his or her income from any source, and his or her ability to pay the judgment, so that the creditor can determine whether they have anything that can be collected upon or not. The debtor's failure to comply is punishable by contempt.
For example, just because they are not working doesn't mean that they do not own a home or land that a creditor may be able to place a lien on. Such would prohibit them from being able to sell the home without paying the creditor out of the proceeds. In addition, the fact that a debtor is not currently working does not mean they don't have money in a checking or savings account that is not exempt, and therefore subject to creditor request for a bank levy and seizure.
Moreover, even if the debtor is judgment proof for now, because he or she is currently unemployed or has no assets, their judgment proof status could very well change in the future. If they do find employment in the future, a creditor may then ask the court for a wage garnishment order. They may also become eligible for collection efforts if they win the lottery, or receive an inheritance.
Judgment debtor examination and related forms can be found in the form books of the legal section of the library, sometimes directly from the clerk of the court, or can be drafted for you by a local attorney.