Trying to find friend add date?

I usually make notes when I add/accept friends, but I somehow missed doing so for someone. I tried to look back at our match histories and see if anything matched up, but it's pretty difficult to do with active players. Is there any way to find an add date or do some search with both our summoner names? In the long run, it doesn't matter, but I am curious as to why we added each other. Neither of us can remember.