Patriots 33 Bills 24, November 19th 1989 In Foxborough.
https://www.pro-football-reference.com/boxscores/198911190nwe.htm
We were visiting family who lived in Massachusetts at the time for Thanksgiving and I talked my dad taking me to the Bills/Pats game that coincided with the trip. This was long before I lived in Western New York so a Bills game was a dream come true for me. As my handle says I've been a fan since '87 but it blossomed into fanaticism when I was 12 years old in that magical '88 season. So come the summer of '89 when the Massachusetts trip was planned I pestered my Giants fan father in buying tickets to the game and taking the family out to Mass a few days earlier. This was the very strange "Bickering Bills" season. We went to the game with my cousin. The 7-3 Bills jumped out to 24-7 lead on the 3-7 Patriots. I remember being impressed by how many Bills fans were in the stadium and feeling a little bad for the Patriot kid and his dad sitting right in front of me. Then it all fell apart. The Patriots scored the last 26 points of the game. I was so upset that I didn't even speak walking back to the car and very little on the drive back to my uncles house.
Since then I've been to about 100 plus Bills games, just about all at the stadium, including having a 4 year run as a season ticket holder. I'll never forget that first game though. As bitter as it was at the time it's become a very fond memory for me, despite the loss.