I applied online. A recruiter got back to me, and we set up a phone interview. An hour before the interview, I even got an email reminder from the recruiter's email address (though it was likely auto-generated).

At the appointed time for the interview, I received no call. I waited for about 20 minutes and then gave up.

I emailed the recruiter for an update. The next day, the recruiter responded by apologizing that he had thought he had canceled the call and that the position is on hold for the moment.

This has never happened to me in my career and is symptomatic of unprofessional behavior. Interviewees need to make time in their schedule plus put in some prep time, even for an opening phone call. If the phone call was deemed no longer relevant, a cancellation notice should have been sent well in advance.

Nothing was asked as the recruiter "ghosted" the call without any advance notice.