Des...it is too late for this interview but each interview that you have prepares you for the next. The interviewer might have been looking to see if you knew how to ask for help or knew how to work together. If you are working on a floor as an RN you will still be part of a team but you do much of your work independently.
So one example could be how you identified a patient who had psycho-social needs and you brought in a social worker to consult on the patient or...you and a colleague teamed up during your time on a floor to safely move the patient in bed. If you asked your preceptor for more experience (learning to start IVs for instance) you could describe how you initiated that training, helped the IV nurse and gained valuable experience...etc.
If you can't think of something from the clinical environment, you could offer how you organized a group of students to study together on the weekend in preparation for a test.
Obviously you will have to pick things that you actually did but I bet if you think back over your preceptor time, you will be able to identify times where you initiated team work!
Good luck on your next interview!