Hi @Lily601
I don't think there is a way to get the Guidebook back sadly, but it's worth contacting Airbnb. I once deleted an entire House Manual on Airbnb by accident and didn't have a backup copy. 🤥
Since then I have learned to keep a backup copy of larger sections of the listing like House Manual and also copies of my Quick Replies & Scheduled Messages in Word. This also allows me to use the spell check feature in Word in case I misspelled something. Then I copy and paste the text into the Listing Section.
For your Guidebook it's a bit tricker. You can still create your text in Word for each entry, but if you accidentally delete the Guidebook, you'll have to re-create all the entries again. However, you'll at least have your text info that you can cut and paste under each entry instead of having to re-create the text.