Sorry if it seems the Flash drive is a bit of a mystery. As you experienced it, it is not hot swappable . We highly recommend always booting up with a USB stick in place. We save logs on that stick too, should you ever find you need some support.
We did put a system in place that is a bit of a compromise. DexterOS will discover a USB stick within a minute. It doesn’t matter what you do, every minute it will check whether a USB stick is active or not. If you find you booted up without a stick and then want to save to one, just wait a minute before calling the save window.
This is something we may revisit in the future, based on user feedback. In the meantime, always booting with a stick is your best bet.
I hope this helps in clearing up the behaviour.