Was Solomon a Child of God?

Solomon the idolator was also an elect child of God saved by grace.

Some time ago a Christian brother recounted a conversation he had with a NeoCalvinist minister. After bringing up Solomon as an example of a Child of God that clearly did not conform to the Lordship Salvationists doctrine of total commitment, this brother was surprised to hear the minister suggest that "we don't really know for sure if Solomon was a child of God."