Also, SD cards are really really sturdy. You can drive a car over them, and I know from experience they can survive a fire.
Maybe if he'd use a micro-SD, he could swallow it. Or hide it pretty much anywhere cause it's the size of a fingernail. Dump the empty micro-SD/SD-adapter into one of those typical "computer paraphernalia" boxes always found on any desk, you know, the one that also contains an aged USB stick, three paperclips, a PS2-USB adapter, post-its, ear-phones and some USB cable, and nobody will expect a thing.
Well a couple of years ago, my house burnt down. I was "lucky" with only a melted flatscreen monitor and further mostly just smoke damage (which insurance still reimbursed as total loss, yay), my flatmate, where the fire started, less so. His part of the apartment, the next day, pretty much was a blackened cube with bits of black debris on the floor, what used to be furniture, his computer, books and audio equipment[1].
In the rubble we found his camera, which was of course useless if not because of the heat[2], then because of the water damage from the fire-fighters.
Inside was a 2GB SD card and it still worked.
So yeah, if for some strange reason you can't keep your backups off-site, nor in a fire-proof safe, store them on a SD card in a camera :-)
[1] He also wasn't insured, making the story even sadder. Fortunately he just landed a pretty good job, also he met his current girlfriend while staying at his parents until he found a new home. So some good came of it, I suppose.
[2] Glass windows melted, can you imagine? Looks like icicles. I later asked a glassworker friend, she said that means it must at least have been 800 degrees Celsius.
Maybe if he'd use a micro-SD, he could swallow it. Or hide it pretty much anywhere cause it's the size of a fingernail. Dump the empty micro-SD/SD-adapter into one of those typical "computer paraphernalia" boxes always found on any desk, you know, the one that also contains an aged USB stick, three paperclips, a PS2-USB adapter, post-its, ear-phones and some USB cable, and nobody will expect a thing.