Could an endoscopy detect that i smoke?

No: Endoscopy is meant to look at the anatomy of the esophagus, stomach and duodenum (or the colon, using a different kind of scope). Smoking may cause changes in the mucosal lining, including inflammation (gastritis, duodenitis, esophagitis) but these aren't specific to smoking. Smoking is 'detected' by history, smell of tobacco smoke on patients, and sometimes urine cotinine (nicotine's metabolite).