I had the same problem after downloading scipy from a .dmg. I uninstalled, and then reinstalled from source: http://sourceforge.net/projects/scipy/files/scipy/0.12.0/ and then the openmdao installer recognized scipy.
This may be useful (from INSTALL.txt in scipy-0.12.0.tar.gz):
To test SciPy after installation (highly recommended), execute in Python
>>> import scipy
>>> scipy.test()To run the full test suite use
>>> scipy.test('full')
Please note that you must have version 0.10 or later of the 'nose' test framework installed in order to run the tests. More information about nose is available on the website__.