Short answer, yes. Long answer: when dealing with ancient history there is always a risk of getting the facts wrong. However, sometime we just do not have the luxury of more than one source amd, in those circumstances, we are left with a dilema: to trust or not to trust. The sixth century Byzantine author, Jordanes, for example makes reference to many tribes in late antiquity, especially the early history of the Goths and the Huns. Now many events can be crossed referenced, but there is still a large debate on how much of Jordanes' narrative is true and how much is false. It will be a long time before there is any agreement on some of the arguments.

But if you mean that historians mistook a work to being entirely fictitious as a form of history, that is less probable. Historians are a critical bunch and there is usually some amount of evidence to corroborate the validity of an account. But its definitely not impossible. It is, on the other hand, definitely possible, as previously mentioned, to mistaked fictional accounts or polarized anecdotes as facts. There is, indeed, an ongoing debate surrounding the 3rd century Historia Augusta and whether it was a history or a mock history.