It may have been somebody who knows you have a boyfriend and knows it would be inappropriate to just come out and declare his affections. Of course, sending romantic flowers signed "your secret admirer" is just as inappropriate. But it sounds as if you've been getting a lot of immature and inappropriate male attention. I would just ignore it and put it out of my mind if I were you. If whoever it is ever comes forward and speaks to you directly, you can just tell him to his face that you have a boyfriend you're not interested. If he doesn't, you don't have to think about him again.