Each court is required to keep track of the length of time that it takes for a case to be resolved from the time that it is initiated. Accordingly, the courts do not want to leave cases open indefinitely. Therefore, once a case is complete, the court will "close" the case. This is for statistical purposes only.
In Maryland a custody case is always subject to modification until the child reaches the age of 18 and has graduated from high school or the age of 19 if the child has not graduated from high school.
Based upon the facts in your question, your wife still has custody because the original court order was never modified. Absent a modification of the original court order, that order is still in force.
I assume from the fact that you are asking about custody, that you and your wife have again separated. If this is the case, then you should consider filing for a divorce and as part of the divorce action request a modification of the custody order. Alternatively, you can simply request a modification of the custody order. You will need to show a change of circumstances and that it is in the best interests of your child for you to have custody.
There are a number of procedural matters that will need to be dealt with. I recommend that you retain an attorney to assist you with this matter.