Can a doctor tell if a nose job was ruined by cocaine use?

Cocaine sometimes can damage the septum, and it's not hard to tell when one examines it.  Even if you get away with it, you would only be putting your own health at risk to go under anesthesia while using.  Honesty is your best safety mechanism.

Hi,
Chronic cocaine use can have devastating effects on the nose. The first significant change is that the mucosal lining of the nose becomes scarred. This leads to poor blood flow and eventually the mucous lining and the cartilage die and this results in a perforation of the nasal septum. Symptoms of a perforation include whistling when breathing through the nose, nose bleeds, lots of crusting and nasal obstruction. The nasal septum is also a support beam for the nose and a perforation can cause the bridge of the nose to collapse causing a significant cosmetic deformity. 
Best,
Mehdi Sina, MD

Hello and thank you for your question.  The
best advice you can receive is from an in-person consultation.  Cocaine usage can cause severe damage to the nose, including saddle nose deformity.   I recommend
that you seek consultation with a qualified board-certified plastic surgeon who
can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon

Cocaine usually damages the mucosa of the septum and can cause a septal perforation.It is important to give full disclosure to your surgeon before undergoing surgery.

Most probably yes. the question is: use of cocaine PRIOR to a nose job or AFTER a nose job? In both cases, yes , use of cocaine is and will be detrimental to your nose (not to say about your overall health). it will compromise the healing process with risk of necrosis.