Can't mount disk with manjaro partition from live flash drive

[gigas002]

I needed to restore system with timeshift, but after selecting the needed tmeshift, it lost my btrfs device and system freezed at once, so I had to hard reboot. After reboot grub seems to be corrupted, so I couldn’t boot into my system, and I had to use live flash drive to restore it.
Here’s list of my partitions:

NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0         7:0    0    93M  1 loop /run/miso/sfs/livefs
loop1         7:1    0 867.5M  1 loop /run/miso/sfs/mhwdfs
loop2         7:2    0   1.9G  1 loop /run/miso/sfs/desktopfs
loop3         7:3    0 921.4M  1 loop /run/miso/sfs/rootfs
sda           8:0    1   7.2G  0 disk 
├─sda1        8:1    1   3.8G  0 part /run/miso/bootmnt
└─sda2        8:2    1     4M  0 part 
nvme1n1     259:0    0 931.5G  0 disk 
├─nvme1n1p1 259:1    0   300M  0 part 
├─nvme1n1p2 259:2    0 922.4G  0 part 
└─nvme1n1p3 259:3    0   8.8G  0 part 
nvme0n1     259:4    0 476.9G  0 disk 
├─nvme0n1p1 259:5    0     1G  0 part 
├─nvme0n1p2 259:6    0    16M  0 part 
├─nvme0n1p3 259:7    0   468G  0 part 
├─nvme0n1p4 259:8    0   641M  0 part 
└─nvme0n1p5 259:9    0   7.3G  0 part 

and fdisk output:

[manjaro manjaro]# fdisk -l /dev/nvme1n1
Disk /dev/nvme1n1: 931.51 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: WDS100T1X0E-00AFY0                      
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 7B1CC2C0-8792-9F4A-BE2E-AAEA216C9DA9

Device              Start        End    Sectors   Size Type
/dev/nvme1n1p1       4096     618495     614400   300M EFI System
/dev/nvme1n1p2     618496 1935065125 1934446630 922.4G Linux filesystem
/dev/nvme1n1p3 1935065126 1953520064   18454939   8.8G Linux swap

But when I try to mount the /dev/nvme1n1p2 or /dev/nvme1n1p1, it says:

[manjaro manjaro]# mount -o subvol=@ /dev/nvme1n1p2 /mnt
mount: /mnt: mount(2) system call failed: No such file or directory.
       dmesg(1) may have more information after failed mount system call.

Meanwhile in dmesg:

[  322.875171] BTRFS: device fsid 9561de22-96e5-46aa-9810-bb027c4815e9 devid 1 transid 329581 /dev/nvme1n1p2 scanned by mount (11423)
[  322.875606] BTRFS info (device nvme1n1p2): using crc32c (crc32c-intel) checksum algorithm
[  322.875611] BTRFS info (device nvme1n1p2): disk space caching is enabled
[  322.947711] BTRFS info (device nvme1n1p2): enabling ssd optimizations

[gigas002]

At least some progress: I managed to mount with mount /dev/nvme1n1p2 /mnt, but since this was an btrfs device this is… odd? And I still can’t mount /dev/nvme1n1p for /mnt/boot/efi,
And I can’t create a chroot here:

mount: /mnt/proc: mount point does not exist.
       dmesg(1) may have more information after failed mount system call.
==> ERROR: failed to setup API filesystems in chroot /mnt
umount: bad usage
Try 'umount --help' for more information.

It looks like I don’t have a @ directory on that device anymore… But I still have it into timeshift-btrfs/snapshots directory.

[gigas002]

So… I just tried to do a silly thing: copy-pasted the latest timeshift’s @ into the root directory, rerun timeshift into live flash, restored it and the system seems to work again