Ziyech was in Paris on deadline day to complete a loan move to PSG but the deal collapsed after Chelsea failed to file the necessary documents in time.
The Parisians have accused Chelsea of negligence and claimed that the Blues twice sent them incomplete or wrong documents before sending the right set of files but by that time the window had closed.
The Moroccan could now spend the rest of the season at Chelsea and McCoist stressed that he needs to accept his current reality as soon as possible.