Problem
You would like to (re)-install passenger after a system wide rvm installation, but you only have the mod_passenger.c file and not the .so after the gem installation.

Solution
Make sure that after using gem install passenger you also use the command to install the apache2 passenger module:

passenger-install-apache2-module

you should then be able to see the .so file and add it to your /etc/apache2/mods-available/passenger.load