If you don't have multipathing set up properly for the SAN the AIX system may see the old FS via the old path.

Also I dont think exportvg is destructive. It just cleans out the AIX ODM. You can always do an "importvg" to bring the VG back, just point it to the hdisk. I use this to migrate the VG from one AIX server to another. Data is still there on disk.