bundle update seems to be deleting my .gem file

bundle update seems to be deleting my .gem file

I am new to building gems, so bear with me.
Scenario:
[Gemfile]
source 'https://rubygems.org'
gem 'curriculous', path: '/mydev/curriculous'



$ ls /mydev/curriculous
Gemfile Rakefile curriculous.sublime-project
Gemfile.lock bin curriculous.sublime-workspace
LICENSE.txt curriculous-0.0.1.alpha.gem lib
README.md curriculous.gemspec spec



$ bundle update
Fetching gem metadata from https://rubygems.org/.........
Fetching gem metadata from https://rubygems.org/..
Resolving dependencies...
Using curriculous (0.0.1.alpha) from source at /mydev/curriculous
Using bundler (1.3.5)
Your bundle is updated!



$ ls /mydev/curriculous
Gemfile Rakefile curriculous.sublime-workspace
Gemfile.lock bin lib
LICENSE.txt curriculous.gemspec spec
README.md curriculous.sublime-project



Question: where did my .gem file go? What am I doing wrong?