Block storage attached but does not appear in file system

I'm having the same problem as described here.
The answer given there, which I understand as basically to follow the instructions for creating a file system on the volume, does not work and seems not to apply.
Specifically, the volume I created some 12 hours ago shows as attached to my linode in Linode Manager. I'm logged in as root to my linode using Lish. I started off trying to make a file system on volume as per the instructions given me:

root@localhost:~# mkfs.ext4 /dev/disk/by-id/scsi-0LinodeVolumemyvolume
mke2fs 1.44.1 (24-Mar-2018)
The file /dev/disk/by-id/scsi-0LinodeVolumemyvolume does not exist and no s.

Aha. A mystery. I've run the following terminal commands and get the following results:

root@localhost:~# ls -lah /dev/disk/by-id
total 0
drwxr-xr-x 2 root root 80 Jun 7 16:56 .
drwxr-xr-x 5 root root 100 Jun 7 16:56 ..
lrwxrwxrwx 1 root root 9 Jun 7 16:56 scsi-0QEMUQEMUHARDDISKdrive-scsi-disa lrwxrwxrwx 1 root root 9 Jun 7 16:56 scsi-0QEMUQEMUHARDDISKdrive-scsi-disb

root@localhost:~# df -h
Filesystem Size Used Avail Use% Mounted on
udev 968M 0 968M 0% /dev
tmpfs 200M 4.9M 195M 3% /run
/dev/sda 49G 5.6G 41G 12% /
tmpfs 997M 0 997M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 997M 0 997M 0% /sys/fs/cgroup
tmpfs 200M 0 200M 0% /run/user/0

root@localhost:~# fdisk -l
Disk /dev/sda: 49.8 GiB, 53418655744 bytes, 104333312 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk /dev/sdb: 256 MiB, 268435456 bytes, 524288 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

My conclusion: the volume is truly lost. How can I get it back?

Edit: I'm running Ubuntu 18.04 LTS