A.H.
I would not push it too far, but I would ask why the snack was not passed out. Tell them your daughter has been really looking forward to it and has kept you abreast of her daily snacks.
As for the teacher eating one - how can you really be certain it came from the box you brought in?
Also - you should ask to make sure no one in her class has an allergy or if the parents mind their child having this type of treat. (I am not big on my son having dairy this time of year and I limit his intake, especially when ill... and creamcicles do contain some dairy.)
If it was a case like this, then I would request that it be returned. However, as these do not cost a ton - I would consider it a gift if the center kept them and I was happy with the care provided.