I am currently an employee for Lowe's and I know exactly the situation you are dealing with. I am currently a cashier at a Lowe's in my city and I deal with my fair share of returns any given day. You can return any item you purchased (except outdoor power equipment which has a 30 day return policy) with the receipt within 90 of the original purchase. If you do not have your receipt, merchandise credit is given. Usually you will be refunded your money the way you paid for it, with the exception being checks and credit cards. Credit cards have the option of either being credited back to the card (takes up to 15 days) or merchandise credit. Checks on the other hand, have a 15 wait period on them so if you decide to return an item before the 15 days, a merchandise credit is issued.
Whenever I have a customer come back to return an item that was paid for with a check, I look and see if it has been 15 days since the purchase. If it has I proceed with the refund as normal. If not, I let the customer know that since it has not been 15 days, the refund will be in a store credit. I then explain to them that if they DO NOT wish to get store credit, come back when the 15 days are up and get a cash refund. I have done this in plain view of managers and have never been reprimanded for it. The returns cashier should have let you know that you would receive store credit and that if you had any problems with that, you could come back later to return your item for a cash refund.
Once you are issued store credit, there is usually no way of getting cash from it. I haven't seen a manager cash a store credit card in all my 3 years of working there. Just like the other rebuttal said, the 2nd purchase was an entirely different purchase and since store credit paid for it, store credit is refunded. The way refunds work is that the compute reads the way it was paid for and automatically shows how you are to be refunded. This is when I say, "it's going to be X dollars and cents on a store credit card/cash/credited back to your card, is that all right with you?" This way if they have any questions about why they are getting a store credit, it's not too late to back out and tell them to come back in X days to get cash.
Many a time has a customer been angry with me because it wasn't until after the store credit had been issued and a manager had told him he couldn't get it cashed out. So I have learned from that mistake and now I tell them BEFORE anything is actually refunded to wait the remaining days and come back. The whole "don't pay with a check" is crazy! If you think you might return something and you paid with a check, wait the 15 days. It's stated right on the RETURNS POLICY board right in plain view at the returns desk.