I truely hope you have some good news soon. My cat had disppear for 4 weeks and then, one day, re-appeared. He never left us since then, although he is still able to come in and out as he wants.
My malamute, on the other hand, was an escape artist since day one. Despite invisible fence system, he would run away on a regular basis. I have quite a few stories on how he came back home (5 or 6 rescue from strangers in a 4 year period). One day, he disapeared yet again and we never heard anything again. He was micro-chipped and had tags on his collar. Also very people friendly. After a couple month I told the boys that he would not come back and we should not wait for him. They asked what happened and I did not make a fairy tale story. I explained that he had a good life but since he did not come back he was likely dead. The boys were sad but I believe kids feel it when grown ups lie to them.
If I don't really know myself, I tell the hypothesis that I truely believe in all the while explaining that it is what I believe but I'm obviously not sure.
We now talk about our malamute without being sad. I don't feel awkward because I'm not hiding anything and the boys sense it. No matter what their questions are, I try to be age appropriate but truthful.
Keep us posted and don't lose hope yet. It's been only a few days.