<human>: Can you provide a brief overview of the text?

We're both in out mid 20's, and met on a dating site. I found him to be funny and attractive and a little awkward, so I gave him my number, unprompted (which I've never done before). We texted for a few days, maybe a week. We talked about art and movies and books. The conversation was light and interesting, and a little flirty without being overtly sexual.  After not too long, I felt like I could connect with him. I invited him to do something this weekend and he was so excited. He had said more than one time that he really wanted to meet me. He even invited me to an event in a few months. Anyway, he said he'd see if his schedule would permit us to get together this weekend. I last heard from him 5 days ago, when we were talking about plans before bed. I replied to is last text in the morning and then sent him something a few days later and got no reply. I'm actually a little shocked. His personality seemed so not this way, and he was into it. Before this, he would (to my surprise) be apologetic for not returning texts after a few hours during the work day (which I could not care less about).  I know I should let it go,  but part of me wants to send him one last text and just to let him know that I really dug him and am confused. 
Is it possible he's got something going on? He genuinely seemed thoughtful and kind an intelligent, and I'm usually great at intuiting what kind of person someone is. Should I just let it go? Sorry for the long story. It's 3am and I couldn't sleep.
<bot>: talking to a guy who went from wanting to meet me to not returning my texts, literally over night. Should I just let it go?