I am conducting several usability tests this week on my sports website. The purpose is for me to find out any flaws in the design or any usability issues that may affect navigation and other factors.

During a research session, I found that it's not a good idea to lead the participant on by saying "did you notice X feature?" during the test. Would these sorts of questions be acceptable after the test is complete?

For example if I have a "contact us" button on the header of each page. But the participant didn't see it and instead clicked on several other links to reach the "contact us" page. Would it be good practice to ask why they didn't do it as intended, or is that something that I should try to conclude by myself?