session variable for request.referer doesn't actually store the url value

ApplicationController.rb

class ApplicationController < ActionController::Base

  protect_from_forgery                                                                                                       

    #session['user_return_to'] = request.url    
    def after_sign_in_path_for(resource)
      sign_in_url = "http://localhost:3000/users/sign_in" || "http://onvard.com/users/sign_in" || 
      "http://www.onvard.com/users/sign_in" #url_for(:action => 'new', :controller => 'sessions', :only_path => false, :protocol => 'http')                                            
      if (request.referer == sign_in_url)

        session[:current_path] || env['omniauth.origin'] || request.env['omniauth.origin']  || stored_location_for(resource) || root_path       
      else
        request.referer
      end
    end


  private
  def store_location
    session[:page_a] = request.referer
    session[:current_path] = "http://localhost:3000" + request.fullpath
    
    puts 'aaaaaaaaa below is page a, which should be missions_path'
    puts session[:page_a]
 #looking at log, this displays the missions_path at first, but after the user is logged in, it changes to 'user/sign_in'. I still can't get the session[:page_a] to store an absolute value.
    puts 'aaaaaaaaaa below should be votes'
    puts session[:current_path]
  end

end

MissionsController.rb

class MissionsController < ApplicationController

  before_filter :store_location
  before_filter :authenticate_user!, :except => [:show, :index] 
  
  def vote_for_mission
    @mission = Mission.find(params[:id])
    @originalpage = session[:page_a]

    puts 'vvvvvvv22 below is original page that should be missions_path, not user sign in'
    puts @originalpage
    #looking at the logs, @originalpage stores user/sign_in
    puts session[:page_a]

    if @mission.voted_by?(current_user) 
      redirect_to @originalpage, alert: 'You already voted on this mission.'
    else
      @mission.increment!(:karma)
      @mission.active = true
      @mission.real_author.increment!(:userpoints) unless @mission.real_author.blank?
      
      current_user.vote_for(@mission)
      redirect_to @originalpage, notice: 'Your vote was successfully recorded.'
    end
  end
end

z Logs and Description

When I change the "redirect_to @originalpage" to a hardcoded value such as "redirect_to missions_path", it works perfectly fine. That is, it logs the user in, and then performs the vote action, and then redirects back to the missions_path, which is the original page where everything started. However, when I try to store this original page under session[:page_a]&@originalpage, it changes to "user/sign_in"


Started POST "/vote_for_mission_mission?id=1" for 127.0.0.1 at 2012-07-09 21:04:22 +0900
aaaaaaaaa below is page a, which should be missions_path
http://localhost:3000/missions
aaaaaaaaaa below should be votes
http://localhost:3000/vote_for_mission_mission?id=1
  Processing by MissionsController#vote_for_mission as HTML
  Parameters: {"authenticity_token"=>"7z8x8DSXlrYqAgrt7ou65/Q3s4wfenaEInpFgY7Xpeg=", "id"=>"1"}
Completed 401 Unauthorized in 90ms

.....
and then some code that signs user in.....
......

Started POST "/users/sign_in" for 127.0.0.1 at 2012-07-09 21:04:26 +0900
  Processing by Devise::SessionsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"7z8x8DSXlrYqAgrt7ou65/Q3s4wfenaEInpFgY7Xpeg=", "user"=>{"username"=>"kibaekr", "password"=>"[FILTERED]", "remember_me"=>"0"}, "commit"=>"Sign in"}
  User Load (0.3ms)  SELECT "users".* FROM "users" WHERE "users"."username" = 'kibaekr' LIMIT 1
   (0.2ms)  BEGIN
   (0.3ms)  UPDATE "users" SET "last_sign_in_at" = '2012-07-09 12:01:23.068480', "current_sign_in_at" = '2012-07-09 12:04:26.305663', "sign_in_count" = 38, "updated_at" = '2012-07-09 12:04:26.306566', "commit" = '--- []
' WHERE "users"."id" = 2
   (1.7ms)  COMMIT
Redirected to http://localhost:3000/vote_for_mission_mission?id=1
Completed 302 Found in 193ms


Started GET "/vote_for_mission_mission?id=1" for 127.0.0.1 at 2012-07-09 21:04:26 +0900
aaaaaaaaa below is page a, which should be missions_path
http://localhost:3000/users/sign_in
aaaaaaaaaa below should be votes
http://localhost:3000/vote_for_mission_mission?id=1
sssssssss below is original page that should be missions_path, not user sign in
http://localhost:3000/users/sign_in
http://localhost:3000/users/sign_in
  Processing by MissionsController#vote_for_mission as HTML
  Parameters: {"id"=>"1"}
  User Load (0.2ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 2 LIMIT 1
  Mission Load (0.1ms)  SELECT "missions".* FROM "missions" WHERE "missions"."id" = $1 LIMIT 1  [["id", "1"]]
   (0.3ms)  SELECT COUNT(*) FROM "votes" WHERE "votes"."voteable_id" = 1 AND "votes"."voteable_type" = 'Mission' AND "votes"."voter_type" = 'User' AND "votes"."voter_id" = 2
Redirected to http://localhost:3000/missions
Completed 302 Found in 179ms


Started GET "/missions" for 127.0.0.1 at 2012-07-09 21:04:26 +0900
aaaaaaaaa below is page a, which should be missions_path
http://localhost:3000/users/sign_in
aaaaaaaaaa below should be votes
http://localhost:3000/missions
  

====> you can notice that page_a changes after the log in.