It's easy enough for him to disappear in a very real sense, should he wish it. Knowing Washington is on the look-out for him doesn't mean he was going to simply step out of hiding.

The shooting range would appear empty, at a glance. Provided Wash stuck around to investigate, he'd find what he was after.

Moments after a shot was fired directly over his shoulder to hit one of the targets, seemingly out of nowhere. Still. It got the message across. If he was looking for Locus, he was in the right place.