Of course, it's not lost. You should have flashed it (with that etcher), insert into rock64 and use. why did you do differently? I guess, you use an image that has rockchip GPT partitioning with a lot of partitions. it might cause many old utilities to behave erratically, some partitions might have IDs indicating their "special" role on the system, prohibiting a compliant environment to mess up with them. you need some hammer. 
maybe you try armbian with their good old MBR scheme and just 1 partition. try use windiskimager for flashing it and let armbian resize its volume on the first boot. there are also tons of other methods to get your eMMC back to the normal state. for example - insert it into rock64 booted with sd card and fill some first megabytes of the raw device with zeros. with dd. make sure you zero eMMC, not SD card.
maybe you try armbian with their good old MBR scheme and just 1 partition. try use windiskimager for flashing it and let armbian resize its volume on the first boot. there are also tons of other methods to get your eMMC back to the normal state. for example - insert it into rock64 booted with sd card and fill some first megabytes of the raw device with zeros. with dd. make sure you zero eMMC, not SD card.
ANT - my hobby OS for x86 and ARM.
