Question Laptop died, OS partition (C:) missing when accessed via usb

Jul 25, 2020
Hi there,
I had an Acer Predator Helios 300 with a 2tb seagate drive in it with two partitions, (C & D)
after a recent windows update, the laptop would no longer turn on. Essentially a brick.
So I pulled the hard drive out and used an external hard drive case and attachment to make it a USB drive.
When I plug it into the new laptop it shows with only one partition (D) and there appears to be no other partitions in any recovery or partitioning programs.
Im currently scanning it to try and find deleted or hidden files, but that is apparently going to take 5 hours.
It shows as a 1.8tb drive .. with 216gb free, from memory the C partition was about 200gb.
Any thought or suggestions on what is happening here and how I can get to my files?