OnePlus 6T Did "fastboot boot" just delete all my encrypted data?
Full credit to alecxs for this answer. Posting incase anybody else has the same problem in the future.


Download stock image(Mine was oneplus.com/uk/support/softwareupgrade/details?code=9)
Use extract_android_ota_payload-master to split the payload.bin inside the zip
(Method for step 2 https://pastebin.com/RfEHuvu7 , I did this on linux because my linux machine has python2 installed, no other reason)
Flash the boot.img and boot with twrp
(Step 3 https://pastebin.com/Gp9aJq36)