Party's rec_name should not search on bank accounts
The bank account module overrides party's rec_name to also search by bank account:
http://hg.tryton.org/modules/bank/file/tip/party.py#l17
If really desired, I think this could be implemented either on another module or depending on the context because only in very few circumstances will the user want to search the party by its bank account number.
Currently, searching the party by its code (ie. 54321) can return parties that have a bank account that contains that number which is very surprising for the user.