I cant understand the "nastiness" some seem to exhibit! The guy made a mistake and as often as we see this issue on here, why would it be so surprising to anyone? Im sure if this electrician has done work for you before and he is, in fact, a friend.....he will step up to the plate and take care of business. Good luck.
Heck, since he obviously put in a two poll breaker (2/30), when he comes back out to make the repair and pay for the damages, have him add one more wire and put in the regular 50 amp outlet, matching your plug on the MH(wired correctly...2 hots, a neutral and a ground) then you'll have (2) 30 amp 110 volt for a total of 60 amps to your MH.
