Royal Crown and Regal Scepter can be stolen by Krampus and eaten by Eyeplants, that's because they don't have "irreplaceable" tag.
Steps to Reproduce
Spawn Royal Crown, Regal Scepter, Krampus and Eyeplants, you find that Royal Crown and Regal Scepter can be stolen by Krampus and eaten by Eyeplants
Spawn Royal Crown, Regal Scepter, Krampus and Eyeplants, you find that Royal Crown and Regal Scepter can be stolen by Krampus and eaten by Eyeplants
A developer has marked this issue as fixed. This means that the issue has been addressed in the current development build and will likely be in the next update.