Sniffing works but can't find the URL

URL Snooper isn't magic - it detects URLs by looking for the telltale url links in network traffic.

Sometimes it can get fooled by non-standard URL links on pages.

If it can't find a URL on a page, as a last resort you can switch to advanced mode and select "All URLs" from the drop down filter list, and try to identify the non-standard URL.  You can also look at the surrounding context to get a better idea of the problem.