Yes, you are VERY lucky indeed, that you had a defective 30 amp to 50 amp dog-bone adapter otherwise you would be looking at severe damage to multiple electrical devices and thousands of dollars worth of damage.
If you want to use that outlet, than either you or a qualified electrician rewire it to a 4 wire 240 VAC 14-50P 4 prong outlet that will fit your 50 amp RV power cord. The 4 wires need to be the following: 1-ground (G), 1-neutral (W), 1-50 amp Load- (Red), 1-50 amp Load (Black). All need to be 6 gauge.
But more importantly, purchase a Progressive Industries EMS 50 amp unit, either the hardwired version, EMS-HW-50C or the portable version, EMS-PT50X. Those devices will NOT let any defective or errant power conditions into your coach when doing something stupid. You definitely dodged an expansive bullet.