At my school, if we broke the sterile field, as long as we recognized it at the time of doing it, told the instructor we knew we did it, and verbalized that we would change gloves, we were OK.
Kicking you out for your glove touching the sheet seems harsh.
It's going to happen in the real world, and you'll just change your gloves. You're not going to get fired b/c your glove touches the sheet, and you change gloves...
I remember checking off on drawing up meds from ampules...I was nervous and my hands were sweaty and shaky...wound up with a shard of glass in my thumb, dripping blood everywhere!