Religion

The old missionary who had them stole them. I think there's a Commandment or something that mentions stealing.

There's a long tradition of artifact collecting among people who were supposed to have been bringing Jesus to Native American tribes. More often, they brought prejudice and stole the cultures' artifacts in the process of saving their souls.

At least in this case, every effort will be made to return the stolen items. It's one thing to frame some arrowheads you plowed up on your farm field. It's quite another to use a Native American's skull as a fruit bowl. That''s some ugly stuff, right there.