$bean->stored_fetched_row_c, logic hooks and relate fields

Im trying to detect a change in a relationship through a logic hook but I cant seem to get the old value to compare it to the new.

I have a serial number module which has a relationship to accounts

Accounts -> one-to-many -> S_SerialNumber

this is visible in my module view and i can get the relationship data if i query the S_SerialNumber

the problem I'm having is I want to detect if this relationship is changed on an after_save logic hook

My before_save hook captures the data with the 

However $bean->fetched_row does not include the relationship data for me to then compare

If I use the $bean->load_relationship() it only gets the updated data

Anybody know how you compare a relationship between a before and after save logic hook?