[Python] ubuntu: uninstall matplotlib with pip won't work

I'm on Ubuntu and I neeed to uninstall matplotlib, which I installed as an ubuntu package and later upgraded with pip. The usual command doesn't work:

$ sudo pip uninstall matplotlib
Can't uninstall 'matplotlib'. No files were found to uninstall.


What should I do?

Extra info:

~$ pip matplotlib --version
ERROR: unknown command "matplotlib"
me@me:~$ pip show matplotlib
---
Name: matplotlib
Version: 1.4.0
Location: /usr/local/lib/python2.7/dist-packages
Requires: numpy, six, python-dateutil, pyparsing, nose, mock, nose, mock

$ pip --version
pip 1.5.4 from /usr/lib/python2.7/dist-packages (python 2.7)

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