This why, especially in non hiring hookups, I always state my potential availability and ask the same from them in the relative beginning.
If they follow up with asking a question about something else or are too vague, I typically ignore them or follow by saying somethings come up but if they let me know typically when they might be available in the future to hit me back up then and we can work something out.
If someone can't be generally specific about availability at the beginning (now before 4pm, tomorrow mid afternoon, usually weekends, usually daytime, etc) I put almost zero stock in actually being able to meet them.