"I suppose they could have belonged to Ste Anne's, St Vincent de Paul's, or Most Holy Trinity."
Likely St. Vincent as at the time you had to belong to the parish if your house was within the parish boundries. Catholic churches in Detroit were built approximately one square mile apart. This from the days when most people walked to church, so everyone was close to a church. But you couldn't pick and choose your church and pastor.

St. Vincent had a convent ghost, thought to be Sr. Appolonia, IHM. Of course the convent is gone now, as is the church.