Use the adjective hapless to describe someone unlucky and deserving of pity, like the hapless car buyer who gives in to the fast-talking salesperson.
The word hapless traces all the way back to the Old Norse word happ, meaning “chance, good luck.” Combine this with the suffix -less (“lacking”) and hapless means “unlucky” or “ill-fated.” A traveler who goes to Moscow and briefly gets lost on the subway? Just a tourist. A traveler who goes to Moscow, accidentally eats food he is allergic to, somehow loses all his money, and by chance gets on a train destined for Mongolia? Definitely hapless.