"Cost us the game" is when the game is in hand, or close to it. Guarantano made a bad play in that spot that put the game out of reach, but saying it "cost us the game" is unreasonable.
Best case scenario after that play, we are still down 28-19, on the road, to the #1 team in the country, without Bituli, halfway through the 4th quarter. What would be the win expectancy, down by a touchdown and still needing a PAT, a TD, a 2-pt conversion, and a defensive shutout just to tie the damn game? 5% 10%? 20%? It didn't help, but certainly didn't "cost us the game."
You know what else cost us a remote CHANCE at winning the game? Bituli foolishly targeting and missing the 2nd half. Toots foolishly targeting the prior game and missing the 1st half. A backup LB getting drunk and disorderly and released from the team. Wright and Calbert both getting penalties inside the 10 yard line on the same drive. Crappy punting. You get the idea...