Cannot cast spells or teleport - started mid-game

Was playing a solo-queue ranked game on Summoner's Rift. Everything was fine until about 30 minutes into the game, and I could not cast any spells. Neither using the normal hotkeys or trying to click on the spell buttons manually produced any effect. Teleporting to homebase also did not work, either with hotkey or pressing button manually.

Tried to change hotkeys, smart cast, normal cast, and other settings in options. Tried to alt-tab. Then tried closing league's gameplay client and re-connecting. Nothing worked. Then tried Alt-F4, going to Task Manager, and closing out all League processes entirely, and reconnecting -- still did not work.

Finally after about 8 minutes or so of trying everything (and apologizing profusely to team), suddenly was able to cast in game again. I just went into battle without spells or abilities, just to help out team with auto-attack damage and maybe provide a meat-shield. I think I was able to cast after getting a kill on enemy champion in battle.

I was using Pantheon. On Windows 7 64-bit. Have had no issues other than this.

P.S. I don't know if it's possible Riot, but if you could forgive me and my team's loss today for this bug, that'd be great. Game was at 2/4/2016 @ ~2PM PST / ~10PM GMT. Thank you.