I am not sure what was in your dock, but Toodledo is a website that you can access from any web browser. You can create a bookmark in your browser for quick access. There isn't typically something in the dock, but if you had some 3rd party app that syncs with Toodledo, that could be what you are thinking about.
I had a generic icon that allowed me to launch toodledo from the dock. As I recall, I just dragged and dropped the web address into the dock, and it created an icon. That's not working now. Guess I will do the bookmark. Thanks.