To the OP. Only you know if it was LPG. It would be virtually impossible to not detect the LPG odorant in a leakage magnitude which you describe. You need the services of a propane motor fuel repair facility to test and verify the integrity of your system. The excess flow valve (shutoff) obviously did not do it's job if it were indeed LPG leaking. By testing with an electronic "LPG Geiger Counter" minute leaks can be found that would be difficult to impossible to find with soapy water. Time to dig out the Yellow Pages IMHO.