Passing instance variables in REST

Preface - I’ve had a number of posts regarding my bigger issue but trying to break it down into smaller parts.

Here is what I’m not understanding regarding REST - why I’m having a hard time passing an instance variable to another action.
First I added another resource into my routes.
map.resources :searches, :collection => {:userchoices => :get}
In the userchoices I hard coded some conditions on the find(:all). I want to make it dynamic though based on the users choice

which is getting saved in the create function as @search = Search.new

After the save I have { redirect_to userchoices_searches_url(@search)}
but no luck in getting the @search params over to the userchoices actions.

I guess my real question here is why ? and is there anything I could do to change it.

TIA
Stuart