not sure if this was covered in any of the intermediate lessons but i did went through (skim through) the newbies, survival phrases, beginners 1 and 2, but i couldn't find a lesson on "asking for the check" in a restaurant.
the closest was one in the japanese culture class (i think it's episode 10).. but it talks about only the entrance (with the なんまいさま ですか?) and ordering food (with the usage of ぬき).
could i say "おわり" and hope that the waiter or waitress know that i'm done and i wanna pay?