So, there isn't a word for this precise phenomenon (to my knowledge), but you're welcome to coin one. If there's one thing cognitive psychology loves, it's terminology. (Don't get me wrong, cognitive psych is delightful, but it loves its lingo.)
N.B. Related phenomena are the cocktail party effect, and, in the large, figure-ground phenomena, and selection bias. EDIT: And priming. Thanks to python_kiss. (Wikipedia has decent articles on these things, but if you're really interested, go to the library and get a good psych book.)