The set-up you describe is called a "Suicide wheel"....though I can't imagine why....
The experience you had is very common for this set-up.
If you are going to go suicide (freewheel hubs, cog, bb lockring) use old steel hubs which have stronger threads. Also use brakes instead of back-pedal.
You were lucky this time. You may want to think about buying a proper track hub before there is a next time.