Message in Master-detail form or Master Form asking to Save, even while Query the record in Apps R12 Forms 10g

This happens mainly due to post-query Trigger,
Add below line at the bottom of your post-query trigger, it will solve.

--the below will avoid showing message to save even while u query a existing record.
set_record_property(:system.trigger_record,:system.trigger_block,status,query_status);