I had the same result from taking antibiotics.
Unfortunately, it only lasted a few weeks, but during that two-three week period, nearly every symptom of my flare disappeared. It was amazing! I had been having flare symptoms for almost a year and I was practically dancing through the house every day, thinking I had found a cure.
I had my antibiotic while in the hospital for a rectal abscess whose infection made my whole system sick. I think the drug was called zosyn and I received it every six hours for three days. I did get the most horrible yeast infection though during that time. It was miserable and affected not just vaginal area, but all over my buttock area as well.
A few months later, my GI tried me on Flagyl when I told him of my "cure", but it didn't do a thing. Maybe, by that time, whatever it was in my guts that responded to the antibiotic was gone or had become resistant. Maybe ibd makes our bowels easy prey for germs that don't normally cause problems with healthy bowels taking antibiotics clean the bugs out.
Also, since I too was sick when I took the antibiotic in the hospital, I kind of like the idea that someone had that my body's immune system was just too busy fighting on off the new invaders to have time to bully my intestines.
UC since 10/05, first symptoms felt as early 1983