A Serious Issue with Turrets

This has only happened to me once, but there was an issue with the ally top lane turret on Summoner's Rift where either the turret was not taking damage, or the turret health bar did not decrease to indicate that it had taken damage. At the time, I was playing Vladimir and my laning opponent was Garen. The turret did not appear to take any damage for more than a few minutes. When I looked at my Turret's health by left-clicking on it, it's health read 1004/1000.