Favorite item does not display while changing catalog set for an user.

Question

We have developed a webstore running in Commerce Server 2007.

There are two catalog sets called A and B.Both are having same items.
The user has been assigned with catalog set A and then the user has added several items as his favorites.

Then a user is changed from a catalog set A to catalog set B through commerce server manager.
The favorite items page does not display any favorites stored by the user.

I tried to find out where the relation between user and favorite items is stored in the database but I couldn't.

Can anyone explain this?
where and how the relation between user and favorite items is stored?
Is there anyway that we can display the favorite items of the user while changing the catalog set as the items are going to be same?