I work as a mental health professional, but in a different state than IL. Here are the rules/guidelines for IL mental health facilities regarding minors: https://www.illinoislegalaid.org/legal- ... d-transfer
Your child may have the right to refuse to see you, but with IL having both legal and physical custody, are you sure you don't have joint legal custody, which is common? If you do, you may have the right to more information.
Know that a child won't be admitted to this type of facility unless than have been evaluated by a psychiatrist. Your ex can't just send him there. In other words, if he's been admitted, he's very much in crisis and needs psychiatric help.
“There are those that look at things the way they are, and ask why? I dream of things that never were, and ask why not?”