I spent at least 2 hours looking over the Network tab in Web Developer Tools, unfolding code blocks associated with the element, looking for id patterns in the inspector tab, and searching for every *.webp, *.png, etc. image filetype in the HTML. When I was about to give up the search and settle for a screenshot, I decided to saving the website using the Save Page As function and open the file locally to see if the element had a "magical proprietary" loading method that would cause it to be nonfunctional when operating locally.
To my surprise, Firefox Web Developer Tools was finally able to detect the image in the Network tab. I tried searching for the file in the HTML, but got no results. Afterwards, I tried using a Chromium Based Browser (Brave)'s Developer Tools for the same website and was able to detect the file's network activity on the very first try. The non-Firefox Web Developer Tool was also able to locate the very CSS file that coded for and initiated the request for the file. It was even able to locate the same file when the webpage was opened locally. On the other hand, the Firefox Web Developer Tool was not able to identify the initiator at all.
In my humble opinion, I think Firefox Web Developer Tools is in dire need of improvement.