The main reason why a Youtuber's uploaded material stopped appearing on the search lists is due to copyright claims. Obviously some cheap and strict producer worried about his own material being misused.
Where did my videos go YouTube?
Try locating the video in YouTube's "Video Manager". Click on "My Channel", then "Video Manager", then "Videos". Do you see the video you uploaded in there? If so, you can change the privacy settings to make it appear publicly in your channel, as well as make other adjustments.