Q:

Has any chess player ever been banned because of doping?

In December 2008, the German magazine Der Spiegel reported on Vassily Ivanchuk's refusal to provide a urine sample for a doping test. This type of refusal is "treated as a positive test result" (according to the article), but FIDE decided that there was no need for a penalty. 
I am not aware of other similar stories in chess. So has any professional player ever been temporarily banned from playing because of a positive doping test?

A:

The short answer is "No". The long answer is "Don't be silly!"
About a year ago I asked elsewhere if the English GM Mickey Adams (the only English player at the time comfortably over 2700) had to go through the WADA style rigmarole of informing the chess anti-doping officials of a time and exact location for every day of the year where he could be found if they wanted to test him as required by FIDE's anti-doping policy.
A prominent member of the FIDE Qualification Committee replied "I'm not saying you're wrong, but that's news to be. Where can I find it?"
This 73-page FIDE document - FIDE Anti-Doping Rules based on Wada’s Models of Best Practice for International Federations and the World Anti-Doping Code - from 2015 spells out in painful detail what FIDE's "intentions" are.
When I sent him the link this was his response -  "I think the International-Level part refers only to things that FIDE Anti-Doping can do if they want to and in practice don't, but still worth knowing."
So, at the moment FIDE has a suitable IOC-friendly policy on the books but they are only likely to actually implement it if the vast Olympic money bags are opened for chess.

