Stroller/ car seat gate check mess

My husband and I just flew internationally with our 8 month old for the first time. The gate agent on our first flight was very rude and aggressive for no reason, but when the pilots / flight attendants came it was like she had a new personality and was so sweet- odd. She was insistent that we leave our gate checked stroller and car seat with her at the gate vs. bring down to the plane like we have in the past. It never made it to our transfer and then took over 24 hours to make it to our destination. I am very understanding that mistakes can happen but it was an avoidable situation coupled with her being unpleasant from the start. We are quite upset with United as we needed both those things and it caused stress and hardship. Has anyone experienced this? How did United ameliorate the situation?