Question

With God’s help,
Hello, honored Rabbi,
I wanted to ask a question that had practical halakhic implications, and I wasn’t sure how to act. A young man/boy from one of the good yeshivot (if not the best), in first-year shiur (17), sat next to me on the bus, and we talked a bit. After that he asked to look at a few things on my smartphone, because according to him the ride was long and, because of the yeshiva, he had no means of passing the time. He also claimed that he has a phone at home and thinks that this is better.
So I gave it to him and sat next to him, and I saw that most of the time he was watching YouTube Shorts (basically TikTok-type stuff), all kinds of videos, and for the most part he got stuck watching videos of less modestly dressed girls, for example doing splits on water-park equipment and floats, or men hitting on them, etc.
In short, I didn’t know what was appropriate to do. On the one hand, I think it’s not necessarily good to restrict viewing and lack familiarity with the world, and that a person should choose his religious conduct out of choice. But on the other hand, there is the issue of “do not place a stumbling block,” and why should that be on my “account”?
So after about 15 minutes of hesitation, in the end I asked for the phone back. But what does the Rabbi think would be appropriate to do?
If he really does have a phone, that sounds even more problematic to me, but it didn’t completely add up to me, because he didn’t seem to know how to use it all that well, and he also said a few contradictory things.