OUI may be found at /mount_point/app/oracle/oui/install, assuming you used OFA.

Within ORACLE_HOME/bin, you may have a link pointing to such. In general, you can find OUI in the app/oracle base directory of the first RDBMS product you installed. Other Oracle products, such as Forms 6i, will have a version of OUI located directly within the ORACLE_HOME directory under the orainst directory. Some Oracle products will use the same installer for multiple products. Oracle9i Developer Suite has an OUI that can be used for iDS and other products (after you upgrade the OUI version using patchset 1 for iDS).

Where to find the oraInventory location? One way is to look in /var/opt/oracle/oraInst.loc and see what inventory_loc references.

If you can rlogin to the server (with appropriate privileges), setting your DISPLAY back to where you are physically located, which assuming you are not using Exceed/etc. and are on a UNIX box yourself (which has a CD-ROM drive), why not mount your local CD-ROM drive so you don't have to run down to the server room?