How to make SQLite trigger modify existing string

I have an SQLite table with a STRING type column named "NOTES". I want to create a trigger that automatically updates the content of the NOTES column, but doesn't replace it entirely.

The following does not work, I do not see errors, the NOTES column just never gets updated.

CREATE TRIGGER AlterNote 
    AFTER INSERT ON MyTable 
    FOR EACH ROW 
    BEGIN UPDATE MyTable 
        SET NOTES= NOTES || 'DATEMODIFIED: ' || date('now')
        WHERE rowid=NEW.rowid; 
    END;

This does work presumably because I am no longer referencing the thing I'm updating:

CREATE TRIGGER AlterNote 
    AFTER INSERT ON MyTable 
    FOR EACH ROW 
    BEGIN UPDATE MyTable 
        SET NOTES= 'DATEMODIFIED: ' || date('now')
        WHERE rowid=NEW.rowid; 
    END;

Is there a way to do this? Basically NOTES=NOTES+"blah"