Twrp is in the recovery partition, which is not the same partition the boot loader resides in.



Since the only way to lock the boot loader is via fastboot, and since you successfully did this, we know your boot loader is working. Get back into the boot loader and unlock your device. You can enter the boot loader via hardware key combination. Also, you can enter the boot loader even if the phone has no is and no recovery since it is independent of those.