Charlie Sheen Fans Stick It To 'Two and a Half Men' Producers

Charlie Harper is gone ... but not forgotten -- especially by some die-hard Charlie Sheen supporters who have been slapping "Where's Charlie?" stickers all over L.A. in what seems to be a silent show of support for the former "Two and a Half Men" star.

The stickers began to appear on various street signs in L.A. within the last few days -- with most of the stickers showing up in the Mulholland area where Sheen lives.

We're told Sheen has seen the stickers and appreciates the message -- but doesn't support the vandalism.

So far, the identity of the sticky bandit remains a mystery.