Usually, trust falls are part of group-bonding exercises to help individuals believe in and trust one another. However, you’re best off doing these activities in a safe place where everybody knows what’s happening. You should definitely not do it off a desk during a party – especially not if you’re the boss!
I’m not sure if nobody saw the guy fall or if they just didn’t feel like catching him. If it’s the latter, then it really goes to show how much the coworkers hated this guy. In America, approximately 1 in 5 people loathe their boss, so don’t feel strange if you’re someone who hates yours.