IDCAMS DCOLLECT D Type records have information of all cataloged and uncataloged generations.
If you are dealing with only 1 GDG,
1. Perform a IDCAMS DCOLLECT "to get only D type records"
2. browse the output file and do a FIND ALL 'GDG BASE NAME'
3. manually find the generations that are in DCOLLECT but not in ISPF 3.4 dataset list.