I have one child to look after and I've
left things behind at the zoo, museum, movie theatre, etc. because I forgot the kid brought it with us.
On a field trip the only thing I expect the teacher to return to the school is my kid (and everyone elses too, of course).
The hoodies and jackets that go to school are the ones I got at the thrift store....anything that's detachable for any length of time, actually.
Nor am I going to harshly punish the kid.
I may make the kiddo backtrack all around to help look, but kids forget things...especially when their mind is on a special day out of school and around friends.
Heck, I had to backtrack around the other day to find my cell phone; I'm an adult and that phone is really expensive. Things happen.
I really don't think this was an issue they had a right to call you at home over...maybe called through the school or stopped by the school.
But, then, really, I don't believe they should put the onus on you!