Receiving lines are definitely becoming passe, unless the couple really wants one. In this instance, if you circulated to talk to your guests (which I would imagine you did during the event, not just plopped yourself in a corner with a plate of food), you're okay. The bride, groom and parents usually 'work the room' casually during the beginning of the celebration, and in most cases, the guests go up to them to hand over a gift and share congratulations when the bride and groom and parents are making their way around the area. It's all very informal and natural, and many guests like having the freedom to circulate and eventually get to the guests of honor and hosts. So you're okay with this arrangement, with how the guests came to all of you.
Most brides and grooms make it a point to visit each guest table to say hello and accept hugs. It an in-person thank-you for their attendance. Parents can do that as well, but most parents allow the bride and groom those spotlight moments at each table.
Don't sweat it. I'm sure everyone was fine with how things went!
Sharon