Sorry after all that I posted above I should have made it clear that you need to take it to a shop and a competent mechanic, who can determine what the problem is and correct it. Don't bother checking the alignment yourself, as the hanger is most commonly bent in, which would NOT cause the chain to unship to the inside, and in addition as you know the derailleur can look/seem OK in one gear combination and not so in others. The hanger could have been twisted, however, as could the derailleur when the chain broke. A hanger can be realigned or replaced. It's best just to replace the derailleur if that's the problem - usually too much labor to attempt to straighten out a twisted derailleur, with no guarantee of success. The shop should first check the derailleur hanger, then the derailleur itself. It's actually quite easy for most mechanics to tell if there is a twisting type issue by just pivoting the derailleur back and seeing if the angle of the pulley assembly changes.

BTW for you and others who post here: It is critical that we have full information, especially what else happened or was done when a problem began, if we are to help you efficiently. Diagnosis is a form of detective work, and we need all of the evidence available, even if you aren't sure it's relevent.