On the horns of a dilemma....

I'm just not quite sure what to do. Today, I went to see a woman who I know primarily in a professional manner. She has a son a year older than the bug hunter, and they like to play together during our visits. Because of the season, we took them small gifts; a homemade necklace and a Bakugan. The bug hunter didn't know for sure that his friend liked Bakugans, but boys in a certain age range seem to find them irresistible, so he thought it would be a good gift. And, he was right; the boy has a small collection and loves them, too. He had his collection with him, and the bug hunter saw one that he didn't have and wanted, and they started talking trades. Finally, I took them both back to the house so the bug hunter could get his collection and they could make some deals. My boy has a big heart, and he ended up trading 2 for 1 on several of the little orbs; he ended up with 3 or 4 new ones, while the friend netted 7 or 8. Finally, I took them back to the shop, and they proceeded to tell the mom about their trades. The bug hunter was going to show a couple of his favorites to her, but he couldn't find them, and an ugly glimmer of suspicion began to work its way into my mind. The friend had really wanted those particular Bakugan, but the bug hunter didn't want to trade them.
When we got home, he looked around, but they were nowhere to be found. Then, he counted out his collection, and even with the uneven trading, he was missing a half-dozen of the best. We searched the house and car, but they are missing, and so is my trust. This boy kept telling the bug hunter that he was SO glad they were friends, and that he wanted to spend the night, and on and on. And all the time, I do believe he was stealing. At the shop, when the bug hunter couldn't find his favorites, I noticed that the friend kept putting his hand in the pocket of his jacket, and that it looked a little lumpy. But I couldn't bring myself to accuse him, and even now, I'm not sure how to handle it. Do I call the mom and ask if he maybe misunderstood and thought they were part of the trade? Or do I let it go? I can't imagine letting the bug hunter play with him anymore, and I certainly can't imagine letting him come back to my home and visit. But what about the mom? Does she need to know that her son would actually steal from someone who was supposed to be a friend (and in the meantime also jeopardize his mom's business relationship with the family)? Ugh. Arrgh. I am praying that God will guide my decisions so that, hopefully, the door will be opened for the boy to learn more than "it's better to not get caught". So, what to do? And how to do it? I'm open for suggestions.