[quote name='e hx c a s s']no i mean would they give me more money than they would if i went without te receipt. but i just found out they have a policy and dont return games unless they are within 7 days of opening the game[/QUOTE]
This is not nearly as bad as you make it sound, since their 7 day return policy only refers to used items which are already open, and you can return it for any reason (so long as you don't abuse the policy).
Regarding your initial question, without a receipt, how would they know you bought the game from them? For all they know, you could have stolen it.