Don't know if this is the right place for mentioning of bugs, but couldn't find anything about it in the FAQ.
Bug report: Deleted shots are still visible in your bookmark page. And when clicked upon you go to a random shot, with a mention at the top that shot you wanted to go to isn't available anymore. Thus the problem is that you cannot unbookmark a deleted shot because you cannot reach it; so with time your bookmark page can get cluttered with deleted shots.
Possible solutions: 1. Automatic unbookmark shots which are deleted. 2. Make shots that are deleted available if bookmarked, such that it can be unbookmarked.
For example shot 23450 is deleted / not longer available but still visible in my bookmarks.