r.rb

class Hash
  def values_at_deep(key)
    result = []
    result << self[key]
    self.values.each do |hash_value|
      values = [hash_value] unless hash_value.is_a? Array
      values.each do |value|
        result += value.find_all_values_for(key) if value.is_a? Hash
      end
    end
    result.compact
  end
end

params = {
  :could_be_anything => {
    :could_be_any_level => {
      :server_message => "I want to get this value, which could be anything"
    }
  }
}

p params.values_at_deep(:server_message)