When I Ditched My Friend’s Birthday Party ...

So here's this thing that happened last weekend. I have a friend named Alex who has been my bestie since college and we've pretty much done everything together for the past 7 years. She had her birthday party at an amusement park last Saturday, inviting me among other friends. But there was one problem, I was scheduled to work on Sunday and Monday too... 🙃 I thought about skipping work for Alex’s sake but she's got tons of friends coming over, so I figured it would be fine if I missed the day and just showed up the next. My boss was being kind of a jerk lately, though, making life difficult with last-minute changes to my shift and no real reason why. So that Saturday morning when Alex called me asking where I was because her party had started an hour ago, all I could think about were those work issues... My friend Jake, who works at the same place as me but on a different team, showed up at my apartment that afternoon unannounced and suggested we take a spontaneous road trip instead. He talked about how much fun it would be to visit some wineries nearby, something I’ve always wanted to do, and after just standing in this empty house all day by myself, the idea sounded way better than going back into the office for a whole weekend... Now here’s where things get really awkward: Jake and Alex went to high school together so when he dropped me off at the end of our trip, I ran straight from my car to Alex's birthday party without changing out of my jeans and t-shirt. But by then, she already thought I had ditched her, and all her other friends were giving me this look like I was some kind of flake... So yeah... I’m stuck wondering if it’s too late for me to fix things with Alex? And do people usually think badly about you when you just cancel on a friend's birthday party at the last minute? It felt super selfish even as it was happening, but now that everyone is talking, I'm feeling really guilty. Am I just overreacting here or does this seem like a pretty bad way to treat your friends?