I thought I'd scan the CASRs for you to see if there was any idea how to proceed. No.
I did find however, that you are now guilty of several breaches,
61.345 failing to keeping a logbook
61.355 failure to retain a logbook for 7 years
61.365 failure to produce a logbook (if CASA asks)
You're nicked Johnnie.
MEANWHILE, back in the real world, there must be some other government (non-CASA) regulations about replacing/recreating lost documents like this.
I like the suggestion about photographing logbook pages. Good idea, easier than scanning them.