I think when you look at the INTENT of what mom was trying to do - she meant well.
She thought she would help you, your daycare and make the other kids happy by sharing something. She didn't foresee that her own child would be so upset about it.
I think you handled it the best you could. You really couldn't refuse to give it back so the whole thing sounds sucky but you had no other choice.
I had a daycare family bring in a toy horse that was about 4 inches tall because one of the daycare girls had two the same. I think it was a few months of me hearing from her that it was her horse and that she was the one who brought it to daycare and how she didn't want so and so playing with it that made me regret ever adding it to the toy collection.
I think having parents bring in things is generally not going to go well. The thought behind it is nice but it tends to turn into a problem when a child can stake a claim to something as 'theirs' versus things that belong to the whole group.