search box 'fell' from top bar to sidebar. How to move it back?

For some reason on one of my blogs the search box, which is usually in the top bar provided by wordpress, has ‘fallen’ into the sidebar. It covers the sidebar content. I’ve moved the content down to accomodate it for now but there must be a way to push it back to where it is supposed to be.

This happens only on https://ubuntuisnotscary.com and not on any of my other blogs, like https://leadingfromtheheart.org or https://francais.tracyrosen.com

Any suggestions for me?