External drive uninitialized after changing partition scheme failed

Question

I was recently trying to partition my external drive into two parts, but I seem to have accidentally broken the partition table by trying to make the empty (1.7TB) part of the disk into a new HFS partition using a botched diskutil command. The previous data partition is now not visible on diskutil and does not automatically mount when the hard drive is connected.

Here is my current output of sudo gpt -r -vvv show /dev/disk1:

gpt show: /dev/disk1: mediasize=2000398933504; sectorsize=512; blocks=3907029167
gpt show: /dev/disk1: MBR at sector 0
gpt show: /dev/disk1: MBR part: type=175, start=357082196, size=3341511771
       start        size  index  contents
           0           1         MBR
           1   357082195
   357082196  3341511771      1  MBR part 175
  3698593967   208435200

diskutil list doesn't seem to show the second partition:

/dev/disk1 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *2.0 TB     disk1
   1:                  Apple_HFS                         1.7 TB     disk1s1

When I attempt to quick search for partitions using testdisk, it gives me a message saying that the partition is unrecoverable:

Disk /dev/rdisk1 - 2000 GB / 1863 GiB - 3907029167 sectors

The harddisk (2000 GB / 1863 GiB) seems too small! (< 2000 GB / 1863 GiB)
Check the harddisk size: HD jumper settings, BIOS detection...

The following partitions can't be recovered:
     Partition               Start        End    Size in sectors
>  HFS                       121948 3907149059 3907027112
   HFS                       122197 3907149308 3907027112
   HFS                       122454 3907149565 3907027112
   HFS                       123023 3907150134 3907027112
   HFS                       123280 3907150391 3907027112
   HFS                       123497 3907150608 3907027112
   HFS                       123866 3907150977 3907027112
   HFS                       124235 3907151346 3907027112
   HFS                       124564 3907151675 3907027112
   HFS                       125045 3907152156 3907027112

[ Continue ]
HFS+ blocksize=4096, 2000 GB / 1863 GiB

Any ideas on how to make the data accessible again?

EDIT: I believe the command I used was this: diskutil partitionDisk /dev/disk1 GPT JHFS+ New 512g. It with an error saying it couldn't write to the disk.