You know what they say
The pain bit is optional.
Nobody really knows WTF causes the soreness. There are tonnes of theories but in my opinion there isn't enough research into it.
Of course I could be wrong, maybe they've done some recent research into it and I haven't seen it. Heck they could have done it in the past 5 years and I wouldn't have seen it, it ain't my specialty. If anyone has any scientific info please post it.
You do not need to be sore to get gains. If not sore then perhaps you could have worked out a bit harder.
Note there are degrees of soreness, too. I think you probably should be a little sore, at least.
For me it usually kicks in about 48 hours later and could last a day from then.