When users search on characters we can't search on, we strip them out of the search. But the cue text over the search results imply that we are searching on it, so if nothing is found, then at worst they think there's nothing like that in the Wagn (at best, they're just confused/annoyed, because they know there is).
this ticket was split from from Some punctuation breaks search
Inform the user that we don't search for all of what they typed in. An example for http://wagn.org/search/item:
We can't search for some of the characters you typed in:
:
Card matching keyword: item