https://www.mediafire.com/policies/data_retention.php
Mediafire has adjusted its data retention policies to delete files they consider "abandoned". For unregistered users, this means files that go 14 days without any inactivity. For registered users, this means files by people who haven't logged in for eight months. This appears to be taking effect in January, if emails that people are receiving are any indication.
If you use Mediafire to host your mods and junk, then log in so they don't go up in smoke! But also, think about moving them to another hosting service. Preferably your own paid web hosting, if possible/fiscally responsible. At least then they get to live and die on your terms!
This has been another in the long, annual-ish series of Kinsie PSA threads about your shit being on the verge of breaking.