Bobby Singer kept a number of journals containing hunting lore, which may have inspired John Winchester to also keep a journal of his own. One of them was recovered by Dean from Bobby's house after it was burned by the Leviathans; it is also possible other journals were stored in Bobby's Storage Unit. Garth has possession of the journals when he later steps into Bobby's shoes. After Garth becomes a werewolf and stops hunting, the Winchesters take possession of the journals.
In the alternate post-apocalyptic reality created by Zachariah, Dean visits Bobby's house, which is deserted. Inside he opens a hidden compartment near the fireplace and pulls out Bobby's journal, which contains a photo of Bobby with Castiel, three other men, and a sign for Camp Chitaqua.
In the time since Dean was trapped in Purgatory and Sam quit hunting, Garth took on Bobby's role of helping hunters, performing tasks such as research and providing alibis for them. He had possession of Bobby's journal and it helps him identify the monster in their current case as a spectre - a type of ghost that becomes vengeful because its grave has been desecrated. The entry Garth looks at in Bobby's journal tells them how to dispatch the spectre: "last spectre I ran into rose soon after someone desecrated a nearby grave. Lucked into finding the grave. I salted and burned the bones and the hauntings ended."
When Dean and Sam investigate a case that Bobby and Rufus had worked years earlier, they consult one of Bobby's journals to try and identify what they are dealing with. Bobby's only entry is "Grand Rapids, Michigan... possible ghost hunt with jackass." Later, in a flashback, it is revealed that Bobby didn't complete the entry because Dean called asking for Bobby’s help tracking Lilith.
- Supernatural: Bobby Singer's Guide to Hunting (Official tie-in book)