Who the fuck were these kids that lost their Gameboy battery covers? How does that shit even happen? You just put in the battery, put the door back on and leave it. I've never lost a battery door to anything. I still have that little shield pieces for the link cable. I've had that Gameboy for at least 20 years too.
I remember losing my battery cover for my white GameBoy Advance. But then again, I had a rechargeable battery pack for my GBA so the battery cover was meaningless. Bought a replacement cover though for it a couple years ago since rechargeable batteries, especially third party battery packs, stop working after a few years of use.