Fair. I was just shocked at how quickly he opened it.
PC went off the road to investigate something, found himself in a ditch (failed to notice it while trying to focus on his target). The ditch housed an abandoned foothold trap, his fall luckily saved him from getting caught, but clipped his boot tearing the one side in the fall.
Had it been a complete failure I'd have had his foot caught.
Ah, not seeing a trap makes sense.
This is where I'd check out by having two party members fail a climbing check and take falling damage. To imagine that happening in real doesn't pass the immersion test for me. Having a player cut their hand on the jagged rocks yes, or lose an item in the rough climb yes, suffer a minor scar (per lingering injury table) against the rockface yes etc but 2 characters falling taking silly falling damage and climbing again doesn't work for me anymore.
It's almost never two party members falling, it's one party member climbing to the top and dropping a rope or if they have a climber's kit putting pitons and attachment points for the others. As far as multiple people falling? I had that happen in a session I played recently. The only reason they didn't fall further was that we had taken the precaution of tying off to each other and my barbarian making a strength check to not fall with them. We also made notes to buy a climbing kit or two when we get back to town.
It may not work for you, it worked for our group and was a fun moment. I think that's a big part of what makes D&D popular, that we have significant leeway on how we run our games.
Guards are a possible complication but yes I would need more context to just drop a guard in. If it was a wall being climbed in an urban environment, perhaps being spotted by someone taking out the trash would be more reasonable. I dunno one would need more context on the location and persons normally in the area.
There are a lot of things I'm going to consider as risks but they are not directly related to a failed check for something like picking a lock. There may be other checks that failure leads to other complications. Failing a stealth check is an obvious one but could also be a perception check to notice a nosy neighbor, lack of investigation or information gathering or similar.
The risk will be related to what precautions the characters take, how long they take and the neighborhood and setting. In some neighborhoods if someone spots you they'd just get their buddy and sit on the stoop and watch. In some cases if you're breaking in the neighbors may have sending stones to alert the residents of the dwelling you're entering because the inhabitants are the head of a powerful organization. In others it might be a cause for alarm but it's not like in you can just dial 911 to get help in most campaigns. Whether there is a city guard outside of wealthy neighborhoods is also going to vary wildly, at least in my game.
I just want the result of failure to follow the fiction and failure should never mean the players at a complete loss as to what they do next. Even in the rare case that what they do next is pursue some other objective. At the same time if the cost of failure doesn't logically follow from the failure, once or twice is just bad luck. Happens all the time? It's a game I don't want to play.