I've heard it reported by others on this forum and it's finally happened to me too. After connecting the Mega/PICA to a Raspberry Pi Zero W, attempting a print and abruptly powering off the printer, the display is no longer responsive.
I have a spare Mega/RAMPS around so I hooked the display up to that and same deal, display shows lines of blocks and doesn't respond.
Bummer. Have another ordered and will remove the USB power fuse from my mega in an attempt to prevent this from happening again.