Found the mesa at 5202/71/-9192... pretty far out.
...and then I fall into lava while building my rail line to Lucina. I lost most of my sandstone, red sandstone, a stack of redstone BRICKS, and a lot of coal, gold, and iron. Not to mention ALL of my regular and power tracks. I HAD to stop and mine a redstone deposit... All of my things burned.
The rail line is close to halfway to Lucina, but now I have to break to mine more iron and gold.
Next time I head to the mesa I'm going to setup a second home so we can have an easy warp.