$excerpt = strip_shortcodes($excerpt);
// $excerpt = strip_shortcodes($excerpt);
I am also having this issue and questioned it in another post. In my case, my images disappear from the front page ONLY after I edit the post. If I never go back and update the post, the images will stay. However, if I update the post, the images disappear. I'd really love some help on this, too!
This actually sounds like a different issue... When you go back to the post, are your pictures missing from the WordPress editor (TinyMCE)?
add_filter( 'the_excerpt', 'do_shortcode');
I really don't know anything about php, so when you say to "stick it wherever", I hope you mean it, because I just stuck it right after the other edits I did.