I think a 10yo can be expected to keep track of a costume. I mean, it's not like it's a teeny little trinket or something. Is it possible that it was stolen? I'd have her search high and low for it and if she truly lost it, I'd just say that she had to make her own replacement costume. Not so much of a "punishment", just a natural consequence and a solution. I made a few of my own costumes at that age. They were fun! Once I took a big rectangular box and painted it like a box of movie theater popcorn and wore it. I think I glued some popcorn to a hat too.
Catholic wife to the very best hubby in the world
and mama to four boys:
, and Teddy