Riding in the street isn't necessarily the same as putting in serious mileage at 90+ rpm. And you were most likely standing for a good bit of it rather than sitting and spinning. If I'm putting in 5-10 miles where a lot of it is standing mileage, then I'm fine on some bike with a slammed saddle. If I'm putting in a 25 mile XC ride or 50 mile road ride, I want my saddle in the right place.

Good idea on the going to a shop and getting fitted. It's impossible to do online without seeing you on the bike, and no one will be able to know how a bike feels until you actually ride it.