I did the exact same thing. Make sure you're persistent about it though, the guy tried to tell me "Sorry man we don't price match certain stores like Radio Shack..." I was lmao wtf?, but yeah that method works and I can also vouch for it.
The price match at Wal Mart works as long it's within the same time window. I just got my Dual Shock 3 for 29.99. Granted, they let me buy it for that price reluctantly. Make sure you bring the ad though if you still want to try.