Budget LAS is a licensee but uses the Budget Corporate System. I too had this same thing happen there over a year ago where I used a coupon, it was on my initial contract, but then when I returned it was not on my receipt anymore. Upon examining my receipt they gave me, I noticed a different RA number and also a different daily rate (by very little). I went to the booth in the garage, presented my initial reservation and the initial contract, and the receipt I was given by the check in attendant, and the issue was corrected almost immediately. I did not ask questions but it was clear the clerk knew very clearly how to fix these types of things.