I think the key questions is were you the only author on the abstract? If so, you have less to worry about. If you also put your supervisors down as co-authors (as is often the case with PhD students), then they may be unhappy about having their name against some work that they didn't get a chance to approve (I know I would be in big trouble if I did this!). Don't want to worry you though, you know your supervisors and how they are likely to react.