Sounds pretty real to me and the theory behind it is written up very nicely.
I wonder: would this work the other way round? Take a (stereo) recording of thunder and an exact time measurement between the flash and the first sound and plot the flash from that. If that worked, you wouldn't need a huge high speed camera mounted on a truck in order to record how a flash propagates...
Besides issues like temperature, you'd need to to control for interference from geographic features like hills and valleys. It might work in wide open flat spaces like the prairies of the American mid-west.
If you're interested in this, there was a very good program on PBS's science show Nova a month or two back, called 'the edge of space' or something similar, which involved photography of lightning at altitude and later from the space station, resulting in confirmation that lightning interacts with the upper atmosphere as well as the ground.
The biggest gotcha with a time-based measurement of the thunder is the variability of the speed of sound with temperature - about 0.6 m/s per degree Celsius. Given that thunderstorms tend to involve pretty significant temperature shifts, the temperature can vary significantly along the path length.
