I think Groundspeak have this covered in their knowledge books:
Can I log a find on my own cache? What about when I go back to visit?
It is considered “bad form” to log a find on your own cache, no matter when you do it. The same is true if you re-visit another traditional cache (for example to place or retrieve a travel bug). Use the “post a note” log option to record your visit in these circumstances.
In either case, you’re not “finding” a cache because you already know where it is. Save the smiley face for use when you’ve truly discovered a hidden cache.
