X rays ..
References :

You cannot tell if a person hurts based on X-rays. There were likely many clues you gave to this chiro that led him to the sore area, otherwise it was a guess. Only you can tell a person where something hurts, or a doctor can ask you. The painful areas are often revealed during a history.
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I am a good chiropractor

many good chiropractors have sensitive hands that can detect subtle differences in the feel of muscle tissue, vertebrae differences, differences in skin temperature….any of these can tell the chiropractor where you hurt.
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Possibly by studying the way you move. Most people give away a lot about themselves by the way they walk and move. There’s also the fact that jobs that cause back pain fit into three basic categories, sitting at a desk, standing for a long time, and heavy lifting. Each of these causes a different pain in a different area. By watching you move and asking a few seemingly unrelated questions the chiro can learn where you hurt.

You should know that there is no proof that chiropractors offer anything better than a placebo for back pain and there is proof that chiropractic treatments for anything but back pain are nonsense. Getting adjustments to your back often results in lingering pain and swelling. Adjustments to the neck can result in the same and also nerve damage, stroke, and death.

From Wikipedia:
Spinal manipulation is associated with frequent, mild and temporary adverse effects,[17][18] including new or worsening pain or stiffness in the affected region.[126] They have been estimated to occur in 33% to 61% of patients, and frequently occur within an hour of treatment and disappear within 24 to 48 hours.[127] Rarely,[19] spinal manipulation, particularly on the upper spine, can also result in complications that can lead to permanent disability or death; these can occur in adults[17] and children.[128] Estimates vary widely for the incidence of these complications,[127] and the actual incidence is unknown, due to high levels of underreporting and to the difficulty of linking manipulation to adverse effects such as stroke, which is a particular concern.[17] Several case reports show temporal associations between interventions and potentially serious complications. Vertebrobasilar artery stroke is statistically associated with chiropractic services in persons under 45 years of age, but it is similarly associated with general practitioner services, suggesting that these associations are likely explained by preexisting conditions.[107][129] Weak to moderately strong evidence supports causation (as opposed to statistical association) between cervical manipulative therapy (whether chiropractic or not) and vertebrobasilar artery stroke.
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the question is…was he/she right. Be very cautious of Chiropractors( I am one) do not submit to long term treatment plans or lots of neck manipulation. 6-12 visits will clear up anything a chiro can help
References :
Chiropractor

Chiropractors are specialists who focus on the alignment of the spine.

In medical terminology, chiropractic medicine is based on the idea of subluxation, which refers to the altered position of the vertebra in comparison to the other vertebrae in the spine, and the subsequent loss of functioning that may result due to this misalignment or joint dysfunction.

Chiropractors are very skilled with their hands, and specialize in touching techniques known as palpations. By simply feeling different areas of the spine, chiropractors can often note where the subluxation is taking place and pinpoint likely areas of pain within patients.

Chiropractors may also use X-rays and other pieces of equipment to determine areas of pain, but in your case, it sounds like these tools were not incorporated. As noted above by another user, chiropractors may be able to develop an initial idea of the source of the pain simply by your movements or how you react to palpation.

Have a nice weekend.
References :
http://www.spine-health.com/treatment/chiropractic/chiropractor-examination-and-diagnosis

http://www.spine-health.com/treatment/chiropractic