Turn back; the oasis is probably just a mirage anyway.

Why get excited? You know how mirages tend to appear to those who wish to see them. And you also know that those scorpions were headed in the same direction you would be if you pursued the water. Why take that risk?
You turn around and try to backtrack. Maybe you missed something important. You have been distracted, afterall.
You've nly been walking a few minutes when you see them crossing your path.
Footprints, but they weren't there a few minutes ago, when you passed by there the first time. You're sure of it.You glance in both directions, seeing that the prints came from your left and headed toward your right, in the same direction as the town had been, but significantly further away.
Maybe there was another town, nearby to the first you didn't head to.