No, his wiring diagram was complete. The scope itself has 50 ohm input impedance (if you put it on the appropriate setting); you do not need another 50 ohm resistor. Also, you're showing two "Line" inputs; actually one of them will be ground.
If you have a slow moving dot, you probably won't see much. But if you turn up the scope intensity, put the speed up to something comparable to the suspected rise time of the transient, and then set the scope trigger level so that it triggers only on a transient (that's "normal", not "auto", trace mode), you will see the transient as a trace on the screen, with enough brightness that it persists long enough to figure out how tall it is.
If you need more persistence than the phosphors of the scope will give you, then either you need to build a peak detector circuit of some sort (look through the app notes of some opamp datasheets, or google for it), or you need a storage scope (expensive).