Disappearing Widgets?

I activated the Daleri Sweet theme, added some widgets to the sidebars, and tried to change the information in one of the sidebars, but it ended up in the header, so I then edited the sidebar.php file, and everything on both sidebars disappeared.

Now, no matter what theme I use, I cannot find certain widgets. They are not used in the sidebar, but they are not available in the list of available widgets. It seems the widgets I can’t find (like Calendar) only show up if that particular theme had a calendar on it in the test run.

I liked the Daleri Sweet, and would like to use it, but don’t know how to get the side bars back, and I like the theme I’ve got on there now, called Blue-Hues, but want to put a calendar, and maybe some other things on it.

Can anyone help?