Well done. You got through a massive day. I wonder if that feeling of let down is just the absence of adrenaline after what has been a very exciting period. Not just the big day itself, but the build up as well. Perhaps you'll get a kind of January Blues and would benefit from planning some smaller scale excursion or something so there's something new to look forward to.
I reckon it's pretty normal for people to be focussing on the couple on the big day, so nothing personal with no one asking you specifically how you are. They might have even resisted doing so because it would seem a little strange to do so.
Anyway. At least there are no drunken recriminations to deal with. You didn't do or say anything that you might have done drunk. That in itself is a blessing when I think back to many weddings I've been at.
You did good, and I bet your daughter was very happy that you could support her as you did. Now it's just a case of getting used to normality again, and keeping on top of any feelings of restlessness, irritability and discontentment that might stem from the lack of anticipation after everything being so wedding-focussed for a while. I've heard plenty of parents of brides say that don't know what to do with themselves once the wedding has passed and there are no longer all those jobs to do.
Congratulations again.
BB