On the subject of the vignette, here is what I think we should do:
Step 1) Impose an ultimatum: Tell the shaman to stop the tension by giving each one of the kobolds the possibility to prove their claims during the period of one day. This is likely to be accepted (as it is a good compromise between the incoming punishment and just letting them free). During this period of time, they would be subject to questioning by everyone, and careful vigilance.
Also consider this:
To make the ultimatum, we must first make some doubting to happen. Also, for the tribe to listen, we need to side with what they believe at first. To combine both we could make the shaman criticize the boldness of the statement of the storyteller, and suggesting that, if goods have been stolen, there there would be a lack of them. This will make the villagers or the storyteller check, and, as they dicover that they indeed lack part of them, say that we still don't know who is telling the truth. Then, we say that they have one day to prove their facts.
Step 2) Tell the shaman what we know about him. His reaction was understandable, given the circumstances. We don't want anyone to be punished here.
Step 3) Gather those that we trust: we must make sure to tell the believers that we want no violence here, and a tell a vague phrase to those who are starting to believe: "It trusts that you will act with wisdom. Don't let her down"
Step 4) During the shaman's period to question both kobolds, we tell something different to each one:
-We tell the storyteller that we know that he is telling the truth, yet he must stand in a low profile. The tribe is more likely to punish him, and so he must be cautious with what he says.
-The shaman will confront the thief. She will begin by camly telling him that we know. We know everything. Yet we understand what he did, because we are a part of him as much as he is a part of us, even if he hasn't realized that. Upon the disbelief that it will create, the shaman will describe the place where he stored the stolen goods. She will then say: "If tomorrow you confess your crime, I will ensure that your punishment is lowered. Yours was an act of fear, yet still a crime. Our deity cares for all of us, believers or not, yet justice is going to be dispensed if you don't repent." She will then leave.
Step 5) During the night, we send calming dreams to the whole tribe.
Step 6) No matter what happens, we make the shaman go with the whole tribe to the place where the goods are.
Step 7) At the end of the season, the shaman has to make a ritual, no matter how imperfect it is, to show everybody that we are here and we are responsible of finding the truth in the past, and we explain the thief's motives to steal, then tell everybody that we care for all of them, and that, even if they are not believers, they are welcome in the tribe, because we care for each and every of them. We are a part of them as they are a part of us.