Attempting to amend the last commit causes git branch to lose tracking

Had local git branch which had a commit pushed to remote (github hosted). 

Modified file, Staged file, Chose append last commit.

Push check box was checked.

Expected the commit to success, but the push to fail due to change mismatch. (Then I would go do a force push to pick up my changes).

Got error messages however the branch now no longer tracked the remote branch.