I once had a prospective student--let's call them Cheat--send me a PhD project proposal that was so good I got in touch to ask for a zoom meeting. But the direct communication with Cheat revealed such appalling English skills that I found myself wondering how Cheat could have written the project proposal. So I googled around. Eventually I found a match at the program for some conference--or, like, some departmental events listing boasting about a student--let's call them Goodkins--presenting at that conference. It was very indirect, but the key point was that Goodkins was presenting a project with the same title and similar description as the proposal that I got offered from Cheat.
Because this wasn't a full program with author contact information, but instead some departmental listing, and because Goodkins did not have a student profile on the department web page, I had to get in touch with the department admin team at Goodkins's university and ask them to pass along a message. At length, though, I managed to get in touch with the Goodkins's supervisor, and sent her the proposal, and said 'does this look familiar?'
Long story short, Cheat had done a summer program at Goodkins's university, and Goodkins had shared their PhD proposal to help Cheat draft their own. Except Cheat stole it and sent it to me.
Naturally, I informed Cheat that I had no interest in working with someone who had stolen a proposal from another student. Cheat tried to say that they had misunderstood, they were willing to change the proposal, etc. etc., but I stopped responding.
Gosh, I'm still angry about this. Poor Goodkins. I should look up where they are now; it was an excellent proposal, and their advisor is a very well respected person in their field. I hope they're doing well.