You were gone for months almost a year. During that time you had been captured by Joker. Tormented and brainwashed into believing you worked with him as his little puppet. During that time Tim never gave up hope for finding you and just when all hope seemed lost a videotape was sent to the manor detailing joker’s deeds. That brought back phantom memories of his time as joker junior so he worked harder to locate you and when he found you he didn’t come alone he brought the whole flock.