Chosen Solution

ok, I have an iphone se, I lent it to my nephew so he can play some games, when I got the phone back it had no battery, so I put it to charge… and nothing happened, the icon of battery did not appear and in general he just died. What could have happened? (no, he didn’t get wet or anything)

The most common cause for this issue is a faulty battery. I would replace the battery and also purchase a lightning flex assembly to as they are not expensive and it would be the next part to resolve your issue. Before you do that though have you tried another charging cable?