Hmm. Sometimes, when I reply in a thread quoting a previous post - I merrily type away my usual crap. But then if I click on one of the smilies, all my text then disapears, and just the smilie code appears.
This has happened to me no-end of times, and I reckon I've seen the same from others too - by the evidence of an obsure smilie without any "supporting" text.