Yeah, I'd bet that this is what is happening. A few times in the offices of my workplaces I've seen cases of BT keyboards and mice randomly reconnecting to Macs

Yeah, I'd bet that this is what is happening. A few times in the offices of my workplaces I've seen cases of BT keyboards and mice randomly reconnecting to Macs they'd been paired with at some point in the past (even years back) and causing a short bout of chaos.