^^^
Agreed. Hex edit method is depreciated, uncertain, and doubtful It' *much* easier and less error-prone, to repartition device using backupmenu and any linuxbox/linux liveCD.

Also, your case isn't exactly same as OP - You actually *can* boot, but Your mmcblk0p2 isn't accessible (as eight correctly stated), probably due to screwed eMMC image being flashed.

Summary - flash regular vanilla eMMC, install backupmenu (or, instead, use Rescue OS - this approach require little more knowledge), using it's 'USB mass storage mode: read&write' connect device to linuxbox/liveCDlinux'ed'box, and repartition device to Your liking (I strongly encourage to prepare 3GB partition for Easy Debian, and another one for TrueCrypt - if You're planning to securely store Your private files).

/Estel