adorable, in that case you know you can’t rely on him or count on him. You can only rely on yourself so forget about him. If you can’t give an answer on the spot just tell the client you will have to research it and get back to them. That’s all you can do. Then work on it and get back to them. That’s it, thats the best ANYONE can do. YOU are not superhuman and no one can expect you to be.
Obviously your boss knows that HE is NOT superman because he has to hire all this help to get the job done. Right? Learn from that.