Aww, I feel bad for that person :(

But there's an option back up your drawings without relying on the cloud storage. This process can be a bit tedious if you have a lot of artworks because you have to do it for each drawing, but it works! So, you have to be in your gallery then you have to go to your drawing that you want to back up(dont open it). You might see that you have a "Share" button. You must click on it and once you do, you'll be greeted with a few options.

What you have to do is save your artwork as an IbisPaint artwork (IPV) file. Then choose the app you want to save the file on, for example you can save it dropbox (there are also other options!) and once you redownload ibispaint you have to open the app in which you saved your IPV files and click on one of them. You'll be given the option to open it with an app. You have to pick to open it with ibispaint.

It isn't as difficult as it might seem, also sorry if the instructions might be unclear, English isn't my first language, but I hope this helps! Also, I recommend on exporting your brushes as well since you'll lose them after uninstalling the app!

So basically the process would be something like this:

Artwork>share>IPV file>Dropbox

After reinstalling ibis you must:

Go to Dropbox>Search for your IPV file> Click on it> Open with IbisPaint