Another possibility is that the image you're after is located in an <iframe>. ActiveBrowser.Find only scans the main page, it does not scan any frames contained in that page. You have to specifically target the right frame to get at the elements on it. For example:
> imageList = ActiveBrowser.Frames.Find.AllByTagName<
foreach(HtmlImage anImage in imageList)
// Do something with each image in the list
This will scan the second <iframe> (since Frames is 0 based).
The Chrome Developer tools is great for helping you figure out where an element is and how to locate it. It will show you the live DOM in the browser. You should be able to locate your tracking image and determine which iframe it's located in.
If you can send me a Fiddler trace
of the page being loaded, I'll be able to investigate this as well and give you exact code for finding the tracking image.
the Telerik team