Mom said they were offering 15% credit from a purchase. How to find it?

My mom bought a Samsung TV on 08/14 for $1,999.99. The rep told her there was a deal that she'd get 15% credit , normally it's 10%. She has no idea how to redeem the offer. 1 person told her it'd be on her account. She has no idea what they're talking about. I was able to help her get logged in online and she has the My Best Buy Plus membership. The only thing I see is 250 points gets you $5 and the TV got her a little over 1000 points, which is $20. She went in store for help and they said it could take a couple weeks to see rewards. Does anyone know what promo they offered her or where she should look?