foul ball and runner does not return to previous bag

[32setmsbloriole]

Im looking for some help with a rule that ive never encountered. Runner was on second and a foul ball was hit. The runner stayed on third for 2 pitches then the umpire realized he was on third and called him out for not returning. In all my years of umpiring Ive always been told its the umpires job to return a runner back to previous bag and if they didnt well then in my opinion it was the umpires fault and the other teams for letting it happen so he should be able to stay on the next bag cause the next pitch had been thrown and not be called out, which ive never heard of. AND THIS WOULD BE FOR ANY LEAGUE UP TO PRO. Thanks for any help