According to this bug report bumping locked question to the homepage is by design. I disagree with this, but my question is about different, but related issue. A couple of times and today is one of these I noticed that locked question which is bumped to the homepage is not visible on the homepage of the website:
But still visible in mobile apps, i.e. on iOS:
And on Android:
Since the both apps are affected I suppose that the problem is in Stack Exchange API, instead of than in apps.