Interference-blocked ball

Question
Situation:  R1 at 3B, R2 at 2B and R3 at 1B and one out.  BR hits grounder to F6 who throws to F3 at 1B and the ball goes off her glove and rolls towards the opening of the dugout where the team that is batting is in.  A team member sitting in the area lazily nudges the ball to the side, before R1 scored.  No other defensive player was close to the ball.  Umpire called "dead ball, interference", Batter out and returned all runners.
Could it have been a blocked ball, or fan interference?  Did the umpire call the wrong rule but enforced a correct rule?
What do you think?
Please inclued rule references

Answer
Hi Rick,

part of the def of a blocked ball is a thrown ball that is handled or stopped by a person not engaged in the game.

I have a blocked ball by the offense so the ball is dead and since there was no opportunity to get an out by the defense all runners return to the last base touched at the time of the blocked ball.  But I can't put the b-r back to bat.  I don't think I have any choice but to score R1 and bases are still full.

Offensive players shouldn't touch live balls

Mark