If you are asking how to find a part located in an assembly structure, look at the Select Tools tab on the Edge Bar. Right mouse click in the field at the top, choose a property to search on, enter a value and it will locate your part. You can also make and store persistent searches if you desire/need that.
Sorry, I didn't realize this was the Developer area. I use the new message list on the Solid Edge main site and thought this to be the Solid Edge Q&A.
You can always get the ReferenceKey property of an Occurrence/SubOccurrence. This byte array is persistent and can be used to binid this reference key again to a SubOccurrence/Occurrence later.