Fried eMMC?

[matega]

I have a Pinebook Pro. I did the following:

• I flashed the Manjaro image on the eMMC from Debian running on from the SD card. That rendered it unbootable, it only lit up both LEDs if I tried to power it on.
  
• I concluded that it must have a corrupt bootloader or u-boot on the eMMC, so I removed it. It then booted fine from the SD card.
  
• I did the trick where I reinstalled the eMMC and then switched on the eMMC switch just after the machine started booting. It booted from the SD card and recognized the eMMC.
  
• I then zeroed out the first few MBs of the eMMC in order to nuke the defunct bootloader or u-boot. After a few seconds the machine hung, I though it was because it filled its RAM with IO cache, no big deal.
  
• Since it must have gone past the bootloader already, I reset the machine - and after that it never showed the eMMC drive again. It doesn't show up in /dev, it isn't shown in gparted. Dmesg only shows one line containing mmc1, it's about clock speed being set. I misplaced my USB eMMC reader, so I can't test it using that. I tried using rkflashtool, it shows this:
  

Code:

rkflashtool: info: rkflashtool v5.2
rkflashtool: info: Detected RK3399...
rkflashtool: info: interface claimed
rkflashtool: info: MASK ROM MODE
rkflashtool: info: Flash ID: 00 00 00 00 00
rkflashtool: info: Flash Info:
       Manufacturer: Samsung (0)
       Flash Size: 0MB
       Block Size: 0KB
       Page Size: 0KB
       ECC Bits: 0
       Access Time: 0
       Flash CS:

but it shows the same even if I remove the eMMC. (I had to patch rkflashtool and add the pid of rk3399 because it wouldn't find the pbp) Did I fry the module somehow? How to test it further before ordering (and waiting for) another eMMC reader? (I want to order a new eMMC too if this one is really fried and I don't want to pay for shipping twice)