Runner Hit In Foul Territory - Deflects Inbounds

[biznil]

Any help with this ruling would be appreciated

Runner on 3rd base. Batter hits solid ball just foul down third base line - one hopper right into stomach of runner coming from 3rd.

Runner was about 2 steps off third base, but was in foul territory.

There was no indication runner was out of baseline or that runner was interfering with play in anyway.

Ball hits runner in foul territory and deflects back into field of play (all in front of 3rd base bag).

Official call was dead ball foul and runner returned to third.

How should this play have been ruled? Offical rules only really state that runner is out if hit in fair play other than obvious interference if foul. Cannot find anyting stating whether or not ball bouncing off runner back into field in front of 3B bag results in play becoming live.

many thanks