From http://www.softball.org/umpires/clarifications_2009_july.asp

We recently received some questions about what bases should be awarded to runners who have missed a base and the ball goes into dead ball territory. Other organizations have specific rules about going back to touch bases that have been missed after the ball is dead. Our rules allow, by umpire mechanic and rule, to let runners finish their base running responsibilities which can allow runners to return to touch a base missed or left too soon after a ball enters dead ball territory.

Play 1: With one out, B2 hits a fly ball to right field which F9 scoops up and throws to F3. The ball is off the mark and enters the 1B dugout. B2 is beyond 1B on the way to 2B when the ball left F9’s hand but missed 1B when passing it. The base umpire calls a “dead ball” and tells B2 “You are awarded third base.” B2 continues to 2B, touches it and is half way to 3B when the coach yells to B2 to go back and touch 1B. B2 retreats, touching 2B then continues to 1B and touches it. B2 then turns around and touches 2B and then 3B. The defensive team appeals that B2 missed 1B and that B2 can not go back and touch it during the dead ball. What is the ruling? RULING: Because B2 advanced and touched 2B which was an awarded base, B2 may not legally return to touch 1B. The appeal is upheld and B2 is out for missing 1B. (Rule 8, Section 5G)