My spellbook got destroyed by water, and the DM decided that was enough for my spellbook to stop working. This means that my Wizard will need a new spellbook, but I still have several spells prepared. I've found a new spellbook on a Wizard we encountered and I now have their spells. Does a prepared spell allow me to copy it back into a spellbook?
Kind of related: What can a wizard do without a spellbook?