If there are views or synonyms created that refer to the remote tables, this is normal:
Suppose you've got a session in DB1 and you issue the following command (assuming you have the rights):
SQL> CREATE view remote_view AS
2 SELECT *
3 FROM table_1@DB2;
View created.
or
SQL> CREATE synonym remote_synonym for table_1@DB2;
Synonym created.
You'll see, not all objects you can access are necessarily yours. You can check this by querying user_tables for the table_name that you don't think should be yours.
MHE