Pink Ward bug

I saw the enemy thresh ward baron so I went over and pinked it right at the edge and it didn't show his ward. I thought hm guess I didn't put it close enough (even though I thought I did). So because I had another pink in inventory I put the pink ward directly over where baron nasher is, and it still didn't show the enemy ward in the pit.

Luckily the enemy team didn't steal baron, but they still had vision which pissed me off. I have had this happen to me in the dragon pit also where I place a pink (in the proper place) and still don't find wards in the vicinity. I asked anyone in the game if they had video footage but nobody did. The enemy thresh thought it was funny, because he saw what happened too. lol. We won the game but that doesn't really matter, it's just frustrating and I hope riot knows that their is a bug with pink wards not finding wards right now