Sacrificial Freshmen (2011)

Two high school students named Silas and Babs wake up from a party they attended the night before only to find out that the party happened five years ago and every student who attended disappeared. Trapped by unstable characters obsessed with solving the mystery of the party and hunted by unspeakable horrors, Silas and Babs must survive and escape or else share the fate as their fellow classmates.