Yes, if your tank isn't covered completely it always has a chance of happening. I've had a feisty fuzzy dwarf lion jump out of the back of my tank. It just comes with the territory.
One of my false percs. took a flying leap a couple of months ago. There was a small section of my tank that was not covered and he somehow managed to find it. I was devastated........needless to say, my display is no longer open for jumping!
Last week my long nose hawkfish found a 2"X3" opening in my canopy and went carpet surfing...
I've been wondering what the hell posesses a fish to jump out of a perfectly good tank???