Lending Money to a Friend-Then He Swore on the Quran

Assalamu alaikum everyone, I’m really just trying to wrap my head around something and need some honest advice or a different way to look at it. Over the last year, someone I genuinely thought was a good friend borrowed about $2000 from me. Just recently, he came back asking for another $500 and swore he’d pay me back by last Friday. This time I had a bad feeling, so I even asked my 12-year-old daughter what she thought-she told me straight that he doesn’t sound like a real friend and might just be taking advantage of me. When I said no, he took an oath on the Quran and promised the money would be back by Friday. Friday came and went. Not a word. No money, no update, no explanation. I waited a whole week before reaching out, and now it looks like I’ve been ghosted. What stings the most isn’t even the cash at this point. It’s that oath on the Quran. As Muslims, we’re raised knowing how weighty that is. I honestly can’t understand how someone can swear on the Quran so casually and then break their word. Right now I’m frustrated with him, but I’m also mad at myself for ignoring all the red flags because I wanted to think the best of a brother. I just have a few questions floating around in my head. Islamically, how serious is breaking an oath made on the Quran? How can you keep yourself from becoming bitter or distrustful after something like this? Do people really throw around oaths on the Quran or Allah so lightly without fulfilling them? I’d really appreciate any sincere advice. Jazakum Allahu khairan.