Just to be clear, Tumblr is probably not deleting our unfinished posts on purpose - this is more likely a bug in their Android app.
Earlier today I wrote a blog post on my phone, using the official Tumblr app. After I was finished, I decided to wait until I was in front of my computer to publish it, so I could find a suitable picture for the post. I clicked back, and a pop-up asks me if I want to save the post as a draft, or discard it. Like the pop-up shown in this picture:
I obviously click Save.
Here's the bug though, it was not saved. I checked my drafts both in the app and on the Tumblr website, but my freshly written blog post was nowhere to be found:
I tried to recreate the problem, and it is in fact happening every time. Except when I went into the post settings and checked Save as draft and clicked Save:
So that's a workaround for now. Hopefully Tumblr will fix this bug ASAP. In the mean time, bloggers be aware!