A:The 'lost gospels' are those non-canonical gospels such as the Gospel According to the Hebrews, the Gospel of Peter, the Gospel of Philip, Gospel of Thomas, Infancy Gospel of Thomas and many others. It should be born in mind that these attributions are no more reliable than are the attributions of the canonical gospels to Matthew, Mark, Luke and John. For scholars, the most important of the non-canonical gospels are the Gospel of Thomas and the Gospel of Peter.
A search of the internet will access English translation of some of these texts, and the are also available (with difficulty) in printed form.