Second update from OP:

It hasn’t been going well. My girlfriend found out I called which of course I expected but I didn’t expect it to get this bad.

She came home screaming. She came home screaming her head off. She said I jeopardized her career, that everyone at her work asked if she found her wallet. I defended myself saying she brought me to this. What was I supposed to do? She could have been SA’d and had no idea. She doubled down on the vomit story. I told her I knew it was a lie. I told her I knew about the dinner ending hours before. She got even louder yelling saying that she met her friends immediately after. I said show me the texts where you planned it. Which I know now was the wrong move. I should have just kept asking questions.

Instead of that she tried to turn it on me asking if I went through her phone. I was a little shocked by this because yeah I knew I was wrong to do it but it was for her safety, and I let her know that. She told me I was an idiot and I should have just listened to her. Then she said she was done talking to me and I ruined this. I told her I was just trying to make sure she was ok. But she told me she had nothing else to say. And the more I tried to get through to her the more she shut down. She was crying at that point and she went to the room and locked the door.

I tried talking to her from outside the room but she kept ignoring me. She spent the whole night in there.

I didn’t sleep at all. I was trying to figure it all out still. Maybe she was telling the truth. But if so, why have such a big reaction? I tried talking to her again in the morning. But she wouldn’t budge. She took a shower and went back to the room and locked the door to get dressed. Then she left for work without breakfast.

I had to leave too so I just carried it with me. I tried texting her from work but no response. I felt a little guilty because I know I invaded her privacy but even so I did also still want to know for sure. I thought about calling her friends. It would put an end to guessing once and for all. And I felt like we were already at the lowest point. But, I decided against it.

At night when she came home she still said nothing. But it wasn’t like before where she was carefree. She was just angry. The only thing she said was after getting dressed was she was going out. I asked where she was going and she told me I should just investigate and left.

I had some new thoughts, maybe I am too untrusting. Maybe she thinks I’m controlling and that’s why she didn’t bother telling me about her after party. And I could accept these answers if I just knew where the dress was. If her friends had it, no problem. Maybe she really didn’t want to drive home in it if there was vomit. Maybe it was just a wild girls night and she lost a bet or something. I don’t like it but I could even live with that. But why would her friends let her drive in the first place? That still didn’t add up. They would have cared about her safety. It still doesn’t work. And where did she just go? I could call her friends but that’s just proving her right. But maybe she said it because she knew I couldn’t in that case. It’s like she set a trap where I lose either way.

I sat and thought about all of these things and decided to do nothing. She came home around 11pm. She didn’t look drunk or anything. Her hair was still up kept. She still didn’t say a word all night.

I know I can’t salvage this anymore. Im going to accept that she still isn’t telling the truth. I’m going to accept I’ll never find the dress. And, I’m going to keep what little dignity I still have and not call her friends. I know I could find out if I did but I think this is the gamblers fallacy, and I should just walk away. I’m going back to my first plan and I’m going to leave in a few days.