(aka Autumn sage or salvia greggi). it was my favorite, too! And it got water! Second plant in that location to die, so maybe it's a bad juju spot.
How much water, and how often?
And how long had it been in that spot?
Even 'drought tolerant" plants need to be pampered the first year or two.
For me, knowing how to treat new plants is the toughest problem in the Southwest. Many xeric plants will die if overwatered, but will also die if underwatered. How can I tell? Yes, I check the ground to see if the soil is dry, but I'm having perennials and shrubs die off even with careful pampering.
So far my salvias have held up, and s. greggii performs the best of all. Wish I could say the same of the lavenders which are supposed to be easy here in NM.
It was on a drip system. I find it hard to believe that I gave it too much water, though.
I ask again ... "How much water, and how often? "
A drip system is not a magic plant protection device. It's just as easy to kill things with one as it is to care for them.
I planted two more in a different location. We'll see!