It is perfectly acceptable to ask for information. His lack of a response could be due to a couple of things. One (most likely) is that he is just busy and this has low priority for him. The other, of course, is that he feels you should be able to find the answers yourself based on the phrasing of the question you asked.
If it has been less than a couple of weeks, I think you can still expect an answer. You can always follow up, of course, but not too soon.
You might also be able to get an answer you need from anything published at the workshop. It might be good to start that in any case.
And, BTW, a post-doc is probably chuckling a bit to be considered a "senior" person. They feel pretty far down the pecking order, actually. But even full professors can be asked, and will often reply.