I'm sorry you lost your gramma, that's sad.
I agree with the others, 7 years old is an age where you should be able to talk to this boy about stealing and hurting other people. Maybe if you can deal with it properly and explain it to him he will return the toys. What if you talk to the entire group about it and tell them you are going to put out a little box in the morning and hope that the toy will come back to the daycare and be put in the little box and nobody will be in trouble THIS TIME. Just an idea, but maybe it would work.