That seems to indicate a catastrophically low bus factor--people get sick, take vacations, sleep, quit, etc. If you’re blocked on an IC doing anything other than finishing their task you've got a bigger problem than them going out of pocket for a day, fix the real problem.

(If they're a manager/decisionmaker of some sort then they better learn how to multitask online, which is like a 30 year old skill requirement at this point)

I have been in some type of team lead/architect position for almost 10 years now. 4+ years at product companies and 5+ in consulting companies. At any given time, I might have needed a decision to be made by my CxO, the client or another team.

On the other hand I might be preparing for a meeting, in a meeting, on a plane, at a customer’s site etc. On the opposite end, there is always a list of things I need to get done. I put that item as “blocked” and move on to my next item. If it is a downstream dependency as a developer, I mock it out and keep going.

If you are dependent on one person to answer a question, what happens when they go on vacation or if they are otherwise unavailable? I make it a point to not be a single point of failure.

Also, I keep my calendar up to date, including time I need to do “deep work”, when I’m traveling for business, of course meetings automatically show up. Anyone is free to put a meeting on my calendar if they need to interact with me synchronously.