Ask Mr. Smarty Plants

There are 10 members of the genus Oxalis native to North America and 6 to Texas, none of which has the common name "pink oxalis." Oxalis is the largest genus in the wood-sorrel family, and the only Pink Oxalis we could find is Oxalis articulata, pink wood-sorrel, native to South America, particularly Brazil and Argentina. Since the Lady Bird Johnson Wildflower Center is dedicated to the use, protection and propagation of plants native not only to North America but to the area in which they are growing, this plant is out of our expertise. We can tell you that we found sites that called it an "invasive weed," and know it is very difficult to eradicate from where it is unwanted because of its underground tubers. It is cold-tolerant to USDA Hardiness Zone 8b; Austin is Zone 8a. That's close enough and, in view of the hard freezes we had in the Austin area this year, might have been sufficient for you to be seeing freeze damage. In addition, the wood-sorrels ordinarily die back and disappear as warmer weather approaches. If you don't want it in your garden, due to its invasive nature, you might consider getting it out now, while you have the chance. However, the tiniest little bit of the bulbil from which the plant grows will produce more of it. 

Pictures of Oxalis articulata from Google.