My image dissapeared

You may need to adjust where you placed the page/summary break. And if your content is taken from a 3rd party URL real-time, it may have been changed on that side.

It is a post I created by hand.
I am new to wordpress and I can't find where is the settings for the 'shortcut' post.

Depending on the theme you use it's possible it's displaying the part of the post on the page in question. Displayed part may be selected using either more tag (page break or summary break), auto-generated (in your case) excerpt or just by cropping the original content.
You can add a custom excerpt to each post on the same page you edit the port.

Do you have a link for the site?

I am using Canvas Theme from woothemes.
Do you know if there is an option somewhere or the only way is to manually edit the php code?

I've never used the Canvas theme, but I'm almost positive there isn't a built in option for allowing html in the excerpt. But there should be an option to use a page template that doesn't use the excerpt. Try a different page template if it has them (it should). Look in your page editor on the right side for the Page Template drop down options. Pick a different template and see what happens. If not let me know and I'll try to help you out with the code.

If you manually add the code into the Excerpt meta box on the 'Edit Post' page, you can use html and have images show up.

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