It came from another iPhone sending an URL link. It was just copies from their iPhone and sent to mine.
Shared web pages just open in your default browser, probably Safari. I don’t think those are saved as file.
Depending on how long ago that was, it may still be in your browser’s history.
If you sync your Safari settings in iCloud, then you may be able to search on any of your devices with Safari, including a Mac, if you have that, where more screen real estate may help sorting this a bit easier.
On iPhone, find the bookmarks tab (book pages icon) in Safari. From the pop-up, you should find another three tabs to choose from: Bookmarks (book pages icon), Reading List (glasses icon), and History (clock icon). The History tab would have a list of recently visited webpages. For my iPhone, it currently shows 13 days back.
If you had Show Suggestions turned on for the Start Page (in the tab switcher), then that would show shared pages. Find links shared with you in Safari on iPhone - Apple Support.