Probably going to withdraw him. Trust has gone and they're not offering at useful explanation
They didn't offer a useful explanation because you didn't actually ask. You listened to end of day feedback then left without asking why something happened that left you, as a parent, fuming.
I'm afraid I can't give an enraged, "how dare they" response and report them to Ofsted for failing to meet safeguarding requirements etc because I literally know as much as you, e.g. nothing about what happened.
So what next? You withdraw your child because trust has gone, find a new nursery and withdraw him again because they do something that leaves you fuming (and again you don't ask)
You are your child's voice at this age. He has no one except you to ask the questions as to why he has been "treated" in such a way as a punishment (if that's what what happened)
There is no scenario in this world, where if I felt "bloody fuming" over an incident that concerned my child and his safety and well-being, that I would not question to find out what happened further and question until I was satisfied.
You asked if you were being unreasonable, a handful said no. I'm not the only one who has said they couldn't comment as you don't know what happened. You, by your own admission didn't ask, you then said you wouldn't ask as they would only get defensive so what's the point.
The point is your child and your duty to protect him. There are correct ways to restrain children and they are horrific and forms need to filled out relating to this, which need to be signed by parents and staff. I can't see any situation, and I'm talking as a Nursery Nursery with over 20 years experience and a Nanny, where a 13 month old needs restraining.
I just don't understand why you didn't ask.
You can't get arsey with me. You offered a scenario. I questioned to get more information and you get the hump. Are you always this difficult?