We’ve all been there before, standing in front of our hotel room door and wondering where on Earth that flat, plastic key card went. Maybe it’s at the bottom of your purse. Or stuck to a credit card in your wallet. Or lying, forgotten, on the nightstand inside. At The Curtis hotel in downtown Denver, those days of fumbling and frustration are over — as long as you have your smartphone on you. The pop culture-themed hotel recently rolled out Hilton’s new Digital Key technology for its 336 guest rooms, which allows Hilton HHonors members to use their smartphones as their room key. The HHonors app also allows guests to check in digitally, choose the exact room they want and get notified when that room is ready, bypassing the front desk upon arrival. “We’re expecting that the people who use it will enjoy it,” said Zach Lybbert, director of marketing and sales at The Curtis.