For one PDF file, command-F opens an unusual "Find" window

I haven't seen anything like this before. I downloaded [this paywalled article](https://www.sciencedirect.com/science/article/pii/S0079642520300013) from a university library WiFi (that I don't often use). Later, opened the article in Preview, and when I tried to search for a word by typing command-F a new window opened up for finding text. I have never seen this happen before! [](https://i.sstatic.net/bZHs2BEU.png) Until today, this is what always happened; the usual magnifying glass box expands and the cursor moves to there ready for me to type the search term. It is still available if I click there manually, it's just that command-F has unexpected behavior (for me) for this document. [](https://i.sstatic.net/f5I5kom6.png) I'm concerned - has something in the PDF "hijacked" Preview? Might it be trying to sending my search terms back to the publisher for statistical analysis? MacBook Air 2020 Core i5 macOS: Sonoma 14.7.2 Preview: Version 11.0 (1056.5.1)