I had students do a research project, and I had them submit the final paper in physical form. This removed my ability to run it through an anti-plagiarism program. But, to the surprise of two students (out of 13!), it didn't remove my ability to see what's smacking me in the face.
The first student turned in a paper with a lot of dated references to the Venezuelan political crisis, talking about "in May" and "this Wednesday" about stuff that happened in 2018. Ultimately, though, it was the sentence "You can read our previous report here" that sent me to a search engine. Ten seconds later, I was reading the exact same paper, only this time it was published 10 months ago in the New York Times.
The second student's paper had a section that was in different-sized font, a frequent effect of cut-and-paste jobs. The unusual country list of "China, India, Hungary, and Mexico" allowed me to search for that collection of words and find the original article immediately.
I shouldn't be able to catch 15% of the class cheating just based on a hunch and the first page of Google results. It's not even sporting of them to completely remove the thrill of the chase. It's just insulting.