Ok, I fixed it; the update changed the settings in the customize part and now I found the option to show it again. 
Maybe you want to change that in the theme update anyways, I guess many people will have the same problem...

Hi,

I used to have my main side bar on every page of my blog, including the main homepage (index). I just updated my theme and now it is gone. It's still visible when you click on e.g. a blogpost. I haven't changed any settings in the "customization" part.

How do I get it back? :(

Thanks!

Aileen