<insert soapbox here>
Wow, sure got some judge-y people on here!! I'm not going to comment on whether I think this was over the top or not, just going to state our policy.
I tell the girls, this is OUR room and you know you aren't allowed in here. If you look, whatever you find you will not get. I will take it back to the store, give it to your cousin, or donate it to a needy child.
Now, would I take them back to the store and make the kid do the explaining? Probably not. I have a DD10, who lies A LOT and a DD6, who doesn't lie at all. If I caught one of them snooping and then lying about it, I *might* take them with me when I returned it but I don't think I would make them tell the cashier.
We don't know the background of this kid and his mom. We don't know if he is a chronic liar, we don't know if she has literally tried everything under the sun. We have 2 AMAZING children. They are extremely intelligent, very well behaved (in public, LOL), can't say enough great things about my girls. But we are at our wits end with DD10. She is so scared of getting into trouble for anything, small or big, that she lies about almost everything. And no, we don't beat her or ground her a lot or any of that, so I don't know what she is so scared of. DH says it is because she is scared to be thought less of (he was quite the liar too when younger, so maybe he is onto something there). Right now we are on a "someday you are going to want a cellphone/to go places on your own/a car and we need to know we can trust you for the little things before we can trust you for the big things" kick. We now write down every lie and keep it on a small whiteboard in the laundry room. We had 3 in November and so far none in December. Does this make me Mommy Dearest?
As parents, we have so much we have to deal with we are all just doing the best that we can. For any of us to sit and judge another parent on something this poor woman probably didn't WANT to do, wow glad to know there are so many perfect parents out there who have handled EVERY situation perfectly. Your children must be outstanding children who never snoop or lie or test your limits. Now, if this parent were to come on here and say, "heck yeah I enjoyed doing this, it was fun, serves the little monster right," then sure, get out your judge-y shoes. But the one time I had to really, REALLY punish DD10 (she didn't get to do a sleepover with a friend that she was REALLY looking forward to) I felt horrible about it and so wanted to go back on my word and let her go, but I had to stick to it. So I seriously doubt this woman ENJOYED doing this.
<stepping off my box>