Happens to us quite often if they miss (which they don't often do). I have this totally unproven theory but it just makes sense to me. In the wild if a snake struck and missed totally, wouldn't the prey pretty much take off immediately? So wouldn't it make a bit of sense that a snake's instinct is that if it misses, it's pretty much going to have to wait a bit for prey to either settle down or come back into the area? So being a predator it's likely to regroup for awhile not expecting that it's prey can't actually take off (being stuck in tub after all LOL)

Like I said, totally unproven, not a tad of science on this...it just makes sense to me.