Besides Satan, was Jesus alone in the desert? If Jesus went to desert alone for forty days and forty nights, how could the apostles write about it?
It's not written in any of the four gospels (Matthew, Mark, Luke, John) that Jesus was alone. Someone in a comment below prior to this edit referenced a hymn called "Jesus walked this lonesome valley" - this is an assumption by the composer. Aside from Satan's obvious presence, no further information is given about other witnesses of the event - we could theorize that someone, or even many someones, were present, Jesus was alone and told his disciples the events afterwards, or that he was alone and the Spirit provided the Gospel writers this info. All we have is what is written in the gospels, anything else is just supposition.