First of all, I would like to stress that I am not a cogsci person and I have almost no background in those areas of science.The question is whether there exists a definition of a phenomenon I recently encoutered: A person is shy, but only in confrontational situations - has no social phobia regarding making friends and so on. Furthermore, this shyness is only demonstrated towards strangers, i.e. the person in question has no problem confronting somebody they know. Lastly, the problem occurs only in person, not over the Internet or telephone. All in all, the question is - is this phenomenon described somewhere? And most importantly - does it have a name? Maybe it has already been defined and studied by someone.Meaning of confrontationalBy 'confrontational' I mean 'having different opinions' or 'having to sort out a disagreement'. To provide an example illustrating the problem:After being ripped off at a restaurant (food bad, late, cold, etc), the person prefers to let the whole thing go and pay rather than argue with the waiter (thus avoiding an in-person confrontation). But,If the person were ordering a pizza over a phone and it did not arrive for an hour, they would have no problem calling the restaurant and discussing the problem.I'm not a native speaker :) Hope the above description clarifies the problem a little bit. 
Defining shyness towards strangers in confrontational situations
terminology;social psychology