> You can't just insert yourself into someone else's big wall party if they weren't planning on it; those other climbers would be spending multiple days on the route and would almost certainly not have food, water, and portaledge space for you (not to mention how profoundly rude that would be...). If you were indeed at the mercy of needing strangers to rescue you, a passing party or a rescue party would need to change their plans and retreat with you, which would only really be a good call if your life were at risk otherwise.

yeah, you can, it's called hitchhiking. it's not very common; but it has be done, Lynn Hill talks about it in her autobiography. if the climber hitchhiking is good enough, the new party will be faster in the end.