By signing in you can keep track of your annotations:

If you download the dataset, you may wish to work with only those labels that you add. With the LabelMe Matlab toolbox, you may query annotations based on your submitted username.

Example: If you signed in with the username 'bob', then you can search the database using the command LMquery:

> Dbob = LMquery(D, 'object.polygon.username', 'bob');

This command will return the index structure Dbob which will only contain the polygons annotated by the user "bob".