show all the blocks added to the particular page?
The simple answer is that there isn't such a page. But you can go to the block administration page and see a list of all blocks for the given theme. If there is a 'configure' link for the block, it's a block that was created through the admin interface, so you can go through them to try to find the block in question.

The other thing you can do is examine the HTML to find the HTML id for the block. This will give you an indication of which block it has been added to, or if it was even added through a block or not.