title: Git removed/removing an already merged file without a delete commit
body: <p>I'm trying to figure out how this situation is occurring, a bit of a mystery, related to a file that has disappeared without a corresponding delete commit.</p>
  
  <p>The file was created in a branch and then merged into master, and now somehow is not present in master. When I run:</p>
  
  <pre><code>git checkout master
  git merge my_branch
  </code></pre>
  
  <p>It shows 'up to date'.</p>
  
  <p>When I run, from master:</p>
  
  <pre><code>git log --all --/path/to/file
  </code></pre>
  
  <p>it shows <em>only</em> the initial commit where the file is first created, but it is not actually present in the directory. However, if I checkout the branch itself, the file is there.</p>
  
  <p>So, the file has disappeared from master somehow, sometime, but there is seemingly no associated delete commit.</p>
  
  <p>It seems like this should not be possible. Any ideas or suggestions on how to investigate this would be very much appreciated.</p>