At 54 minutes into the film the survivors retrieve the cellphone that belongs to the killer. They try to call 911 but can't because the phone is locked and password protected. All cellphones even if locked can still call out to 911. It is the only feature that remains unlocked.
When the girl is locked in the bad guy's car after he locks it by remote somehow, the doors are shown unlocked several times while she is honking for help and also just seconds before the bad guy unlocks them by remote to get her.
When the girl reaches for the cell phone after her boyfriend is killed, she gets stabbed in the hand. Before she gets stabbed her hand is over the phone. When she gets stabbed, the phone is no longer there.
What are the differences between the R-Rated Version and the Unrated Version?
A
For the R-Rated Version nearly all gore scenes were substituted by inoffensive footage. Therefore there's no real difference in the running time even though the Unrated Version is far more brutal. A detailed comparison between both versions with pictures can be found here.