Hi,
You can try to recover from an USB drive.
Place the correct JunOS image on a FAT32 formatted USB drive.
Create a junos-config.conf on this drive as well with the following content: (root password is lab123)
system { root-authentication { encrypted-password "$1$qGd4t8fX$pvFswSbgV/5rvLqNY8Ksp1"; ## SECRET-DATA } }
And load the image from this USB drive on boot.
Afterwards you should be able to default the device.
Good luck!