Thought. If all other cards in the set were SN'd and this one card, for whatever reason, never got it then a UER Note1 may be appropriate as well. With the Note2 reading UER: Not serial numbered or something to that effect.
I do caution is before putting a Note2 in, ensure that all cards are like this. There are instances where a card may have missed the SN process so only 1 or 2 cards are missing the SN but all others of tha player do have it. Putting a Note2 wouldn't be appropriate for just one card. A Comment when adding to your collection would be the approach.
Tired and trembling
I am descending,
will I have to stay here
and live this life again?