ticketmaster gem fails to be found in script

gistfile1.rb

Beginning of script:
#!/usr/bin/ruby
require 'ticketmaster'
require 'ticketmaster-lighthouse'
<snip>

Script failing when run:
$ ./lh.rb
./lh.rb:2:in `require': no such file to load -- ticketmaster (LoadError)
        from ./lh.rb:2

But the gem appears to be installed:
$ gem list ticketmaster

*** LOCAL GEMS ***

ticketmaster (0.7.0, 0.6.10)
ticketmaster-lighthouse (0.8.0)
$ /usr/bin/ruby -rubygems -e 'require "ticketmaster"'
$ /usr/bin/ruby -rubygems -e 'require "ticketmasterX"'
/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require': no such file to load -- ticketmasterX (LoadError)
        from /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `require'
        from -e:1

Adding require 'rubygems' did the trick