If you had lived in the time John had reported this, you could have asked Malchus or his decendents "did this happen?" and they would have told you. His name was given (as were many others) by John so that you could have checked. Chances are that Malchus could have been found in a local congregation for John speaks as if any one reading this would have known who Malchus was.
John has a literary habit of speaking of himself in the third person. For instance he calls himself "the one whom Jesus loved". "Another disciple" could be John, it could be James as well. John is no doubt calling attention to Peter purposely by this literary technique however.