In Windows applications instance lists are remembered. To find out where they are kept first find out the "Internal Identifier" of the business object involved, say, BUSINESSOBJ_N.
Then search for files with names BUSINESSOBJ_N_Part_1.Lst and BUSINESSOBJ_N_Part_2.Lst in a temporary directory on your system.
These files store the instance list details of BUSINESSOBJ_N between Framework executions. They can be deleted at any time to cause remembered instance list details to be lost. You should always delete both files (Part_1 and Part_2) together.