N400 question on what counts as detained?

Hi -

I have my n400 interview next week and would like to know what counts as detained?

About 5 years ago I traveled to Bahamas and had both my conditional permanent resident card and my new permanent resident card and on the way back was approached by a border patrol officer on why i had these two cards with me. I explained that one was expired and that I kept them in the same card holder. He took the conditional permanent card and said he mailed it back to USCIS for me and I was free to go, did not sign anything or have anything handed to me.

Would this count as a detention? I did nothing wrong and the officer was very friendly and explained that i should have mailed it back before.