Yes, it sounds as if you are trying to chase down self generated leads on property unassisted. As mentioned earlier, if you are targeting "foreclosures," it's sad to say but this is the treatment that people get...customers and agents alike. You can take all of the excuses offered and put them----. It's neither fair, respectful, polite or professional! You will likely find that in the majority of these cases when your inquiries are not responded to, that there is already a contract in place.......
With this said, consider aligning yourself with your own real estate professional that can take the lead and provide you with good reliable information. By contacting the listing agent you are appealing to someone that already has an established relationship with the seller. It's best that you have your own personal representation and by doing so minimize the possibilities of a conflict of interest.
Thank you for your post.....this is a serious problem and one that should be addressed!