The Miz actually picked up an injury at WrestleMania Backlash, but it happened before his flesh was consumed by the undead.
When Damian Priest opted for a lumberjack match at WrestleMania Backlash, he likely didn't envision the lumberjacks being zombies. The horde of the undead turned out to be almost as problematic for Priest as it did The Miz as both were forced to fight them off at certain points during their match on Sunday night. Lucky for Priest, his night didn't end in the zombies eating him alive.
That's what WWE wants you to think happened to The Miz. The moment The A-Lister was overcome by the lumberjacks has been discussed at length since it happened. Miz also didn't make an appearance on Raw, although John Morrison hinted that he's okay. Miz has also posted a photo of himself looking zombified on social media, assuring fans that he feels great.
Despite The Miz's claim that he feels fine, Wrestling Observer's Dave Meltzer has reported the contrary. Apparently, the two-time WWE Champion tore his ACL during the lumberjack match at WrestleMania Backlash. At this point, it's unclear how severe the tear is, or how long it will keep Miz sidelined. Either way, the injury couldn't have really come at a better time for The Miz.
Since The Awesome One was supposedly eaten by zombies over the weekend, it's probably for the best that he doesn't appear on TV for a while. Whether that be WWE's attempt to make us believe The Miz really is dead - or undead - or he remains absent for so long that most fans forget why he disappeared in the first place. Fingers crossed it's the latter, but odds are some people won't be forgetting that match in a hurry.
As for The Miz's injury, that is somewhat out of the ordinary. The A-Lister suffers injuries so infrequently that he has let it play into storylines in the past. During his heated angle with Daniel Bryan, The Miz mocked his rival, who was retired at the time, for wrestling a style that ended his career for a few years. The Miz is rarely injured, and this tear might be the longest he has ever been out with an injury depending on its severity.