S.M.A.R.T. may not pick up a bad bearing. That is usually a clicking sound. If the bearing is bad enough. Yes it may be picked up. By that time, it may be trashed. Then the disk may not be functioning right. The diag should pick that up.
Give it some time, and see if the sound returns.
I would give the drive a good spin. If you hear the clicking, time for an RMA.