Can't find User model

I have a controller, SubOrder, that my clients use to place orders with
our company. I pass in a userid, which I would like to use to find a
specific user within the controller. Seems easy, right? Here’s the
relevant code (within the create action of the SubOrder controller):

sub_order =
user = User.find(sub_order[:userid])
    def sub_order_params

When I am running my Rspec tests to test the create action, I’m getting
the following error message:

ActiveRecord::RecordNotFound:Couldn't find User with 'userid'=

When I run this exact code in the console, sub_order contains all the
params I passed, and user has the correct userid stored, so I’m not sure
what is going on. The only possibility I can think is that the userid is
a uuid, and I’m trying to find it by string, or something like that?