You need something to verify coolant temp. 15 minutes at idle in the driveway may not have been enough to get the coolant hot enough to open the stat.
You can take the radiator cap off and stick a meat thermometer in the hole and see what happens.
If your coolant isn't circulating by about 190-195 (I see you have a 180 stat but give it a little extra time), your stat is most likely bad or installed incorrectly.