I saw that my older revisions were being deleted on a new site I made and was wondering why... then I saw this in wp-config.php:
define( 'CONCATENATE_SCRIPTS', false );
define( 'WP_POST_REVISIONS', '10' );
define( 'MEDIA_TRASH', true );
define( 'EMPTY_TRASH_DAYS', '15' );
define( 'WP_AUTO_UPDATE_CORE', 'minor' );
/* That's all, stop editing! Happy publishing. */
Were these changes made recently? They are pretty major for me.