Praying for your son. Remember “train up a child in the way they should go and when they are older they will not depart from it”. Your son will return in Jesus Name, call forth the angels of God to watch over him and guard his way. Pray Psalm 91 over him and that his heart will be soften to return to the Lord.
Not sure if you saw this post on the prodigal but there is a prayer at the end as well that may help.