Not able to trace back a removal of a code from a file history in bitbucket.

[Brijnandan Chauhan]

Hello Atlassian,

1. We made a change in a branch via pull request and merged the pull request.

2. In an another pull request we modified and deleted that change which is coming in the history.

3.  But when we see the file history we are not able to trace back the changes that are present in the history. There is no sign of removal in the history of the commits. 

We believe it to be a bug and have seen this twice.  Could you please help us explaining the nature of this bug.

Thanks,