I took a UA flight last week and just go back. I would like to see the details online for this past flight as it ended up with a big schedule change causing me more than 5 hours delay on the road (almost missed a very important appointment). I would like to file a complaint but I can't remember the exact flight segments that I was forced to switch to (UA announced that the original flight was cancelled "while" I am waiting at the gate. In short, it is really a "last minute" cancellation!). I tried using the same confirmation number / ticket number at united.com, but I kept getting back "not able to find" message... Is it the case that UA removed the flight reservation once it is taken?

Thanks