What, exactly, did you install?

Did you install the Instant Client?  Or did you do a full client install?  If you did a full client install, which option did you pick during the installation process-- Administrator, Runtime, or Custom?  If you did a full client install that didn't include SQL Developer, you can always restart the Oracle Universal Installer, do a custom install, and choose to install just SQL Developer.

That being said, my bias would generally be to download the most recent version of SQL Developer from OTN separately.  SQL Developer gets released much more frequently than the Oracle client so the version on OTN is generally multiple revisions more recent than the version that was shipped with the client.  If you're going to be developing code, you may as well leverage all the new features of SQL Developer rather than settling for whatever version was current when 11.2 was released.

Justin

we can't know how/what client did you install

You also can download sql developer from here:

Oracle SQL Developer Downloads</title><meta name="Title" content="Oracle SQL Developer Downloads…

edited: sqldeveloper 4

SQL Developer 4.0 Downloads</title><meta name="Title" content="SQL Developer 4.0 Downloads"…