infield fly

[Bunky]

infield fly rule situation. Runners on 1st and 2nd. Ball is hit 8-10 feet beyond basepath from 2 to 3rd base. Obvious pop put. I heard no ump call in-field fly rule. He says he did(the base ump not the plate ump). He was facing the outfield when he did call it- even he admits to this. I said how do you expect anybody to hear it? Ball was not caught and the only one who heard the ump call infield fly was the boy on second who was near the ump. The runner on first ran to two while the runner on two was off the base about a third of the way to three and went backto two when he heard the ump. The batter was standing on one thinking he was safe. Total confusion. I believe the ump called infield fly rule, however he was not vocal and was not facing the plate. The runner at two was out via the tag and -wham-double play. Can the get 2 out when the ball is dropped on a infield fly rule, or should the runners be placed back a the bases 1-2 with the batter out? Thanks