The problem was almost certainly caused by a USB enclosure that translated a disk's 512-byte logical sector size into 4096-byte logical sectors. This is explained in more detail here.here. If you're lucky, you might be able to restore the partition table by using gdisk
on the disk attached in its original way. See the gdisk
documentation on GPT repairs for general procedures. You'd need to read the backup partition table from the disk and hope that it's still intact.