Couldn't resist checking..my stock recovery I still intact.
i went and tried to boot fastboot from adb, now i can't get anything to show other than the qualcomm crashdump mode, presumably because oneplus set this phone to make you select fastboot from recovery, and since it is not there, the adb command has me stuck in a boot loop. even rebooting it just gets me the same screen lol
edit: if someone stumbles upon this reply in a search and finds themselves in the same desperate scenario i did, the answer is to be very fast with button mashing. first press the volume up and power to get out of crash dump, then the instant the screen goes black, stop pressing power button and mash both volume buttons to get to fastboot