Flash memory is written in sectors, much like rotating disk memory. Whether you write one byte or 512, you're writing the entire sector. If something interrupts that process, you'll lose the sector. An Eggfinder sends around 100 bytes per second, so you'd potentially lose 4 or 5 seconds, and if that data spans multiple sectors you could potentially lose more. Maybe the card jiggled loose... we recommend that you tape it in with some good masking tape (not the low-tack blue/green stuff).