How can I retrieve data from a HDD that couldn't finish os reinstall?

My sister asked me to fix her laptop that couldn't recognise some of the peripheries including the network cards. She hasn't used it for almost a year. First (almost half a year ago) I asked her to make a backup of all her files, but she obviously forgot that and now was in a hurry. So I started the laptop, it booted just fine. Date and time was totally nonsense, couldn't connect to any network, couldn't update drivers manually, so I decided to just reinstall the os. It had Windows 10 pre-installed. The reinstallation started just fine, but around 38% it suddenly got the blue screen of death. After that it wouldn't start, claiming there was no valid boot info on any of the hard drives. At home I first tried using an external Win10 image, but it couldn't recognise the HDD at all. I then tried using Ubuntu ran from a USB stick. Gparted keeps saying that it encounters an output/input error while trying to do anything on that HDD. I since installed Ubuntu onto an external drive, because I had enough having to re-install and re-configure everything all the time; that is sdb with all the partitions. I was paying extra attention not to do anything with the HDD during the process. lsblk lists the HDD with no partitions, but it's at least there (sda). $ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS loop0 7:0 0 63,5M 1 loop /snap/core20/2015 loop1 7:1 0 63,4M 1 loop /snap/core20/1974 loop2 7:2 0 4K 1 loop /snap/bare/5 loop3 7:3 0 73,9M 1 loop /snap/core22/858 loop4 7:4 0 73,9M 1 loop /snap/core22/864 loop5 7:5 0 237,2M 1 loop /snap/firefox/2987 loop6 7:6 0 349,7M 1 loop /snap/gnome-3-38-2004/143 loop7 7:7 0 485,5M 1 loop /snap/gnome-42-2204/120 loop8 7:8 0 497M 1 loop /snap/gnome-42-2204/141 loop9 7:9 0 91,7M 1 loop /snap/gtk-common-themes/1535 loop10 7:10 0 12,3M 1 loop /snap/snap-store/959 loop11 7:11 0 53,3M 1 loop /snap/snapd/19457 loop12 7:12 0 40,9M 1 loop /snap/snapd/20290 loop13 7:13 0 452K 1 loop /snap/snapd-desktop-integration/83 sda 8:0 0 223,6G 0 disk sdb 8:16 0 298,1G 0 disk ├─sdb1 │ 8:17 0 512M 0 part /boot/efi ├─sdb2 │ 8:18 0 205G 0 part /media/oriba/69895ea3-aa89-4618-ab95-a7bd361f9df6 └─sdb3 8:19 0 92,6G 0 part /var/snap/firefox/common/host-hunspell / sr0 11:0 1 1024M 0 rom fdisk now returned this: $ sudo fdisk -l /dev/sd? Disk /dev/sda: 223,57 GiB, 240057409536 bytes, 468862128 sectors Disk model: SATAFIRM S11 Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes That's all; no identifier, no label, no partitions. However, after trying testdisk and photorec (both finding zero files using the smallest sector size) it usually disappears from there as well: first it appears as a disk with 0 size, then it completely disappears until I shut down the laptop and start it again. Here's testdisk: Select a media (use Arrow keys, then press Enter): >Disk /dev/sda - 240 GB / 223 GiB - SATAFIRM S11 Before selecting Quick Search: Disk /dev/sda - 240 GB / 223 GiB - CHS 29185 255 63 Current partition structure: Partition Start End Size in sectors Partition sector doesn't have the endmark 0xAA55 After searching, testdisk returns nothing, so I go to deep search, which also returns an empty list, I only see the headers: Partition, Start, End and Size in sectors. However, if I now type lsblk, it lists sda as size 0: sda 8:0 0 0B 0 disk fdisk doesn't list it anymore, until I reboot. I never tried to write anything onto that HDD, nor did I try to format it. Is there anything else I can do or is the hardware malfunctioning? Also, did I mess it up anywhere (apart from not making a backup)?