In the commands you show you used to install unoconv, there were two options ...
which of these did you use?
cp unoconv/unoconv /usr/bin
# or link unoconv to /usr/bin
ln -s unoconv/unoconv /usr/bin/unoconv
Also, it appears that either one dependent upon where you were located when issuing the commands.
Unoconv is a python script and there should be a reference/listing for unoconv in /usr/bin/
As root user:
ls -l unoconv
To see if it's there.
As far as reference to it in Moodle, it was never a plugin (Emma is correct). There was, however, a setting for the path to unoconv and an option to use Google or Unoconv ... but NOT a separate 'typical' plugin.
Use the Site Admin area search and search for 'path' to find the config area for paths.
As far as what you un-installed from the Moodle Admin interface, did you un-install unoconv in Document Converters?
If so, then I don't think there is a separate download of that code to install as a plugin. You might have to download the code for the version you have, find the fileconverter code, then copy it back to your production server.
Am looking for that now .... but have been un-able to locate. Maybe a true coder/programmer could help us out here
'spirit of sharing', Ken