You bring up a good point. In my area there are three stakes made up of about 24 wards. The youth dances are generally attended by young people from the entire area. These are limited to youth ages 14 to 18. I don't think they have inter stake dances in Salt Lake because there are so many young people in any given stake.
Former Bishop Dixon could have acted as a chaperon at some of the dances in his stake. That duty rotates from ward to ward within a stake and youth leaders within the ward take on the responsibility when it is their turn. The Bishop of a ward is considered a youth leader and usually the Bishop or one of his two counselors are in attendance. This assignment usually rotates as well. Usually about once a year a member of the Bishopric will have a turn to chaperon a dance.
So would there be a chance that Elizabeth could have attended a dance that former Bishop Dixon chaperoned? Not likely because she was only 14 and wouldn’t have attended very many dances. It is also not likely that they would have had any inter stake dances. I’m sure that if Elizabeth ever attended a dance in Dixon’s stake that the family has alerted LE to this. The family’s desire to bring her abductor to justice will not be swayed by anybody’s position in the church.