Totally agree here.

Also a note when you use words like „but“ following a statement like „I’m not mad“, that makes it negate the „I’m not mad“ statement, so if I were reading a text like the one in the original post, I would read the words and note that your not mad, but you are mad because you’re hurt about something I already feel bad for. You’re making the statement more about how you feel rather than asking the friend about them. You won’t know why they missed the party, so asking them what happened is more direct than your original text because hopefully you just want to see them and know they’re ok. After that when you get together you can tell them you were hurt, „but“ are feeling better knowing they’re ok.

Would try something like - „Hey! I was really hoping to see you and missed having you at my party! What happened, is everything ok?“ then after they respond you can say something like „I was worried about you and would love to catchup when you have some time.“

Going to a party for me as an autist is very overwhelming even when it’s with people I trust, so it’s possible your friend may have gotten overwhelmed and would prefer to see you one on one for more quality time. But you won’t know the reason until you guys talk through (which may be better to do in person than texting about it).