With me it happen once the following:
Battery went to 0 and i put it to charge but not using the original charger, after a few minutes 5% and i turn it on and it boot but the battery indicator was at 0% i remove the cable and Mi5 down, connected again the cable and nothing.
Only the original charger boot it up again.
Now i read somewhere that in EDL mode the Miflash tool can recover it, but before going to Miflash and flash anythong see if it detects.