I know this is an older topic but I made exactly the same thing as Dnstje did, and maybe this answer could help other people.
First of all, thanks Rod Smith for the excellent explanation about this issue. I did use your references to solve my problem.
After a long research, I found a software called Active@ Partition Recovery, which is not free but it worth the price. I bought the personal license for $39.90.
At the first time, it found the lost partition with Quickscan but it couldn't be recovered because the Win32DiskImager has created 2 linux partitions: /boot and /.
So it showed me a warning telling me it cannot override the current partitions.
I closed the APR and opened the Windows Disk Manager (Control Panel -> Admin Tools -> Computer Management -> Disk Management) to delete the booth partitions.
Then, opened APR again, did a SuperScan on entire disk, and it did found my "lost" partition again. I clicked on the partition with the right button and clicked Recover. Now the APR show that is possible to recover due to disk had no partition (I leave all default option and clicked on recover button on first tab). But the task was not finished yet.
The drive letter appears on Windows but Windows cannot read information due to corrupted files, so I opened a command prompt as administrator and run chkdsk [drive_leter] /f to fix the disk.
After chkdsk terminates it tasks, I was able to access my files, but all the files at the beggining of the disk was lost (as expect, because Win32DiskImager wrote data on it). It was about 250MB lost, and it's nothing compare to entire disk.
So, I hope this post can help other people wich is facing a similar problema.
Sorry for any english mistakes.