My question involves criminal law for the state of: Wisconsin

My 13 yr old son was caught shoplifting last evening. I am not in any way excusing his behavior. What I am questioning is what happened after he was caught. I found out he was detained only because I called my son asking why he wasn't home yet. When I arrived at the store, I called asking to be allowed in as the store had closed for the evening. I was told to "wait" by the manager - she was "doing paperwork". The police had not yet been called. I was not allowed inside to see my son until the police had arrived - even though it was past 11:00 curfew. In the meantime, the manager had interviewed and searched my son - all while I was there but not allowed inside. Was it legal for her to search and interview my son without either police or parent present? I'm somewhat okay with him being interviewed and searched by police without me present, but very not okay with this going on without a parent or the authorities present.